Displaying publications 181 - 195 of 195 in total

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  1. Effect of operative variables and kinetic study of butyl butyrate synthesis by Candida rugosa lipase activated by chitosan-reinforced nanocellulose derived from raw oil palm leaves
    Elias N, Wahab RA, Chandren S, Abdul Razak FI, Jamalis J
    Enzyme Microb Technol, 2019 Nov;130:109367.
    PMID: 31421729 DOI: 10.1016/j.enzmictec.2019.109367
    Currently, the chemically-assisted esterification to manufacture butyl butyrate employs corrosive homogeneous acid catalyst and liberates enormous quantities of hazardous by-products which complicate downstream treatment processes. This study aimed to identify the optimized esterification conditions, and the kinetic aspects of the enzyme-assisted synthesis of butyl butyrate using immobilized Candida rugosa lipase activated by chitosan-reinforced nanocellulose derived from raw oil palm leaves (CRL/CS-NC). The best process variables that gave the maximum conversion degree of butyl butyrate by CRL/CS-NC (90.2%) in just 3 h, as compared to free CRL (62.9%) are as follows: 50 °C, 1:2 M ratio of acid/alcohol, stirring rate of 200 rpm and a 3 mg/mL enzyme load. The enzymatic esterification followed the ping pong bi-bi mechanism with substrate inhibition, revealing a ˜1.1-fold higher Ki for CRL/CS-NC (55.55 mM) over free CRL (50.68 mM). This indicated that CRL/CS-NC was less inhibited by the substrates. Butanol was preferred over butyric acid as reflected by the higher apparent Michaelis-Menten constant of CRL/CS-NC for butanol (137 mM) than butyric acid (142.7 mM). Thus, the kinetics data conclusively showed that CRL/CS-NC (Vmax 0.48 mM min-1, Keff 0.07 min-1 mM-1) was catalytically more efficient than free CRL (Vmax 0.35 mM min-1, Keff 0.06 min-1 mM-1).
    Matched MeSH terms: Enzymes, Immobilized
  2. Fulltext Meat molecular detection: sensitivity of Polymerase Chain Reaction-Restriction Fragment Length Polymorphism in species differentiation of meat from animal origin
    Ong, S.B., Zuraini, M.I., Jurin, W.G., Cheah Y.K., Tunung, R., Chai, L.C., et al.
    International Food Research Journal, 2007;14(1):51-59.
    MyJurnal
    Three restriction enzymes were used in Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) using the mitochondrial cytochrome b region to establish a differential diagnosis which detect and discriminate between three meat species: pork, cow and chicken. DNA was extracted from samples containing meat of a single animal such as raw pork (Sus scrofa domesticus), chicken (Gallus gallus) and cow (Bos taurus) as well as mixed samples of two species of animals in different ratios. The amplified 359 base pairs (bp) portion of the mitochondrial cyt b gene from pure or mixed samples in different ratios was cut using three different restriction enzymes resulting in species specific restriction fragment length polymorphism (RFLP). This technique proved to be extremely reliable in detecting the presence of low levels of target DNA obtained from a 0.25 mg component in a particular mixed meat sample. This revealed the cyt b region as highly conserved and consequently a good molecular marker for diagnostic studies. Thus, this technique can be applied to food authentication for the identification of different species of animals in food products.
    Matched MeSH terms: DNA Restriction Enzymes
  3. Molecular epidemiologic analysis of Vibrio cholerae O1 isolates by pulsed-field gel electrophoresis
    Mahalingam S, Cheong YM, Kan S, Yassin RM, Vadivelu J, Pang T
    J Clin Microbiol, 1994 Dec;32(12):2975-9.
    PMID: 7883885
    Isolates of Vibrio cholerae O1 El Tor from two well-defined cholera outbreaks in Malaysia were analyzed by using pulsed-field gel electrophoresis (PFGE). Isolates from sporadic cases occurring during the same time period were also studied. Digestion of chromosomal DNA from these isolates of V. cholerae O1 with restriction endonucleases NotI (5'-GCGGCCGC-3') and SfiI (5'-GGCCNNNN-3'), followed by PFGE, produced restriction endonuclease analysis (REA) patterns consisting of 13 to 24 bands (ranging in size from 46 to 398 kbp). Analysis of the REA patterns generated by PFGE after digestion with NotI and SfiI suggested the clonal nature and close genetic identity of the isolates obtained during each of the two outbreaks (Dice coefficient, 0.93 to 1.0). Although they had very similar REA patterns, the two outbreak clones were not identical. Isolates of V. cholerae O1 from sporadic cases, on the other hand, appeared to be much more heterogeneous (five different REA patterns detected in the five isolates tested; Dice coefficient, 0.31 to 0.81) than those obtained during the two outbreaks. We conclude that PFGE of V. cholerae O1 chromosomal DNA digested with infrequently cutting restriction endonucleases is a useful method for molecular typing of V. cholerae isolates for epidemiological purposes.
    Matched MeSH terms: DNA Restriction Enzymes
  4. Colorectal carcinoma in Malaysians: DNA mismatch repair pattern in a multiethnic population
    Cheah PL, Looi LM, Teoh KH, Rahman NA, Wong LX, Tan SY
    Asian Pac J Cancer Prev, 2014;15(7):3287-91.
    PMID: 24815484
    BACKGROUND: The interesting preponderance of Chinese with colorectal carcinoma (CRC) amongst the three major ethnic groups in Malaysia prompted a study to determine DNA mismatch repair (MMR) status in our CRC and attempt correlation with patient age, gender and ethnicity as well as location, grade, histological type and stage of tumour. Histologically re-confirmed CRC, diagnosed between 1st January 2005 and 31st December 2007 at the Department of Pathology, University of Malaya Medical Centre, were immunohistochemically stained with monoclonal antibodies to MMR proteins, MLH1, MSH2, MSH6 and PMS2 on the Ventana Benchmark XT autostainer. Of the 142 CRC cases entered into the study, there were 82 males and 60 females (M:F=1.4:1). Ethnically, 81 (57.0%) were Chinese, 32 (22.5%) Malays and 29 (20.4%) Indians. The patient ages ranged between 15-87 years (mean=62.4 years) with 21 cases <50-years and 121 ≥50-years of age. 14 (9.9%) CRC showed deficient MMR (dMMR). Concurrent loss of MLH1 and PMS2 occurred in 10, MSH2 and MSH6 in 2 with isolated loss of MSH6 in 1 and PMS2 in 1. dMMR was noted less frequently amongst the Chinese (6.2%) in comparison with their combined Malay and Indian counterparts (14.8%), and was associated with right sided and poorly differentiated tumours (p<0.05). 3 of the 5 (60.0%) dMMR CRC cases amongst the Chinese and 1 of 9 cases (11.1%) amongst the combined Malay and Indian group were <50-years of age. No significant association of dMMR was noted with patient age and gender, tumour stage or mucinous type.
    Matched MeSH terms: DNA Repair Enzymes/genetics
  5. Analysis of Hereditary Nonpolyposis Colorectal Cancer in Malay Cohorts using Immunohistochemical Screening
    Wan Juhari WK, Wan Abdul Rahman WF, Mohd Sidek AS, Abu Hassan MR, Ahmad Amin Noordin KB, Zakaria AD, et al.
    Asian Pac J Cancer Prev, 2015;16(9):3767-71.
    PMID: 25987035
    BACKGROUND: Lynch syndrome (LS) is an inherited predisposition to colorectal, endometrial (uterine) and other cancers. Although most cancers are not inherited, about 5 percent (%) of people who have colorectal or endometrial cancer have the Lynch syndrome. It involves the alteration of mismatch repair (MMR) genes; MLH1, MSH2, MSH6 or PMS2. In this study, we analyzed the expression of MMR proteins in colorectal cancer in a Malay cohort by immunohistochemistry.

    MATERIALS AND METHODS: A total of 17 patients were selected fulfilling one of the Bethesda criteria: colorectal cancer diagnosed in a patient aged less than 50 years old, having synchronous and metachronous colorectal cancer or with a strong family history. Immunohistochemical staining was performed on paraffin embedded tumour tissue samples using four antibodies: MLH1, MSH2, MSH6 and PMS2.

    RESULTS: Twelve out of 17 patients (70.6%) were noted to have a family history. A total of 41% (n=7) of the patients had abnormal immunohistochemical staining with one or more of the four antibodies. Loss of expression were noted in 13 tumour tissues with a negative staining score <4. Of 13 tumour tissues, four showed loss expression of MLH1. For PMS2, loss of expression were noted in five cases. Both MSH2 and MSH6 showed loss of expression in two tumour tissues respectively.

    CONCLUSIONS: Revised Bethesda criteria and immunohistochemical analysis constituted a convenient approach and is recommended to be a first-line screening for Lynch syndrome in Malay cohorts.

    Matched MeSH terms: DNA Repair Enzymes/metabolism*
  6. Melatonin improves cognitive behavior, oxidative stress, and metabolism in tumor-prone lethal giant larvae mutant of Drosophila melanogaster
    Wong KC, Sankaran S, Jayapalan JJ, Subramanian P, Abdul-Rahman PS
    Arch Insect Biochem Physiol, 2021 May;107(1):e21785.
    PMID: 33818826 DOI: 10.1002/arch.21785
    Mutant lethal giant larvae (lgl) flies (Drosophila melanogaster) are known to develop epithelial tumors with invasive characteristics. The present study has been conducted to investigate the influence of melatonin (0.025 mM) on behavioral responses of lgl mutant flies as well as on biochemical indices (redox homeostasis, carbohydrate and lipid metabolism, transaminases, and minerals) in hemolymph, and head and intestinal tissues. Behavioral abnormalities were quantitatively observed in lgl flies but were found normalized among melatonin-treated lgl flies. Significantly decreased levels of lipid peroxidation products and antioxidants involved in redox homeostasis were observed in hemolymph and tissues of lgl flies, but had restored close to normalcy in melatonin-treated flies. Carbohydrates including glucose, trehalose, and glycogen were decreased and increased in the hemolymph and tissues of lgl and melatonin-treated lgl flies, respectively. Key enzymes of carbohydrate metabolism showed a significant increment in their levels in lgl mutants but had restored close to wild-type baseline levels in melatonin-treated flies. Variables of lipid metabolism showed significantly inverse levels in hemolymph and tissues of lgl flies, while normalization of most of these variables was observed in melatonin-treated mutants. Lipase, chitinase, transaminases, and alkaline phosphatase showed an increment in their activities and minerals exhibited decrement in lgl flies; reversal of changes was observed under melatonin treatment. The impairment of cognition, disturbance of redox homeostasis and metabolic reprogramming in lgl flies, and restoration of normalcy in all these cellular and behavioral processes indicate that melatonin could act as oncostatic and cytoprotective agents in Drosophila.
    Matched MeSH terms: Enzymes/blood
  7. Mismatch repair genes expression defects & association with clinicopathological characteristics in colorectal carcinoma
    Kaur G, Masoud A, Raihan N, Radzi M, Khamizar W, Kam LS
    Indian J Med Res, 2011 Aug;134:186-92.
    PMID: 21911971
    DNA mismatch repair gene (MMR) abnormalities are seen in 95 per cent of hereditary nonpolyposis colorectal cancer (HNPCC) and 10-15 per cent of sporadic colorectal cancers. There are no data on MMR abnormalities in Malaysian colorectal cancer patients. This study was aimed to determine the frequency of abnormal MMR gene protein expression in colorectal carcinoma in Northern Peninsular Malaysia using immunohistochemistry.
    Matched MeSH terms: DNA Repair Enzymes/metabolism*
  8. Enantioseparation of (R,S)-ketoprofen using Candida antarctica lipase B in an enzymatic membrane reactor
    Ong AL, Kamaruddin AH, Bhatia S, Aboul-Enein HY
    J Sep Sci, 2008 Jul;31(13):2476-85.
    PMID: 18646277 DOI: 10.1002/jssc.200800086
    An enzymatic membrane reactor (EMR) for enantioseparation of (R,S)-ketoprofen via Candida antarctica lipase B (CALB) as biocatalyst was investigated. A comparative study of free and immobilized CALB was further conducted. The catalytic behaviour of CALB in an EMR was affected by the process parameters of enzyme load, substrate concentration, substrate molar ratio, lipase solution pH, reaction temperature, and substrate flow rate. Immobilization of CALB in the EMR was able to reduce the amount of enzyme required for the enantioseparation of (R,S)-ketoprofen. Immobilized CALB in the EMR assured higher reaction capacity, better thermal stability, and reusability. It was also found to be more cost effective and practical than free CALB in a batch reactor.
    Matched MeSH terms: Enzymes, Immobilized
  9. Isolation and characterization of dengue viruses serotype 1 from an epidemic in northern Queensland, Australia
    Blok J, Kay BH, Hall RA, Gorman BM
    Arch Virol, 1988;100(3-4):213-20.
    PMID: 2840873
    Thirteen strains of dengue type 1 were isolated from the lymphocyte fractions of 69 acute phase blood samples collected at Thursday Island Hospital during 1981 and 1982. One further strain of type 1 was isolated from 7 blood samples despatched by air from Cairns Base Hospital during 1982. Four of these Australian isolates representing the beginning, middle, and end of the epidemic were examined by restriction enzyme mapping and were found to be identical for the nine restriction enzymes used. The maps differed from those derived from two Malaysian dengue type 1 strains isolated during the epidemic of 1981-82 in that country. This suggests reliance on serological typing to establish global circulation patterns of epidemic dengue is insufficient and that more specific methods such as genome mapping are useful.
    Matched MeSH terms: DNA Restriction Enzymes
  10. Gene mapping of Malaysian alpha thalassemias with alpha and zeta globin gene probes
    Lie-Injo LE, Herrera AR, Lebo RV, Hassan K, Lopez CG
    Am J Hematol, 1985 Mar;18(3):289-96.
    PMID: 2983536
    Restriction enzyme analysis of the alpha and zeta globin genes was carried out in four cases of Hb Bart's hydrops fetalis, in three patients with Hb H disease without Hb CoSp, in three patients with Hb H disease with Hb CoSp, in 47 individuals with alpha thalassemia trait, and in 47 normal individuals. All four cases of Hb Bart's hydrops fetalis resulted from deletions of alpha 1 and alpha 2 globin genes which did not extend to the psi zeta 1 and zeta 2 globin genes. The same type of deletion was observed in alpha thal1 carriers, but two newborns (one Malay and one of Chinese extraction) had a nondeletion type of alpha thal1 which was confirmed by quantitative alpha globin gene analysis. In addition, two other newborns diagnosed as alpha thal1 trait carriers (one Malay, one Chinese) were shown to have a deletion of both alpha globin genes by quantitative alpha globin gene analysis, but further testing with zeta globin gene probe failed to reveal an abnormal fragment length characteristic of an alpha globin gene deletion. We believe that this last condition is due to a large deletion which includes all alpha globin genes and all zeta globin genes on the same chromosome. On another front, Bgl II restriction analysis of all four Hb Bart's hydrops fetalis cases and the alpha thal1 trait carriers showed a 10.5-kb Bgl II restriction fragment, in the hydrops fetalis as a single band, while in the carriers this 10.5-kb fragment was accompanied by the usual normal 12.5-kb and 11.3-kb fragments. We report that this 10.5-kb fragment, previously thought to be specific for the Southeast Asian alpha thal1 gene deletion, is also common in normal individuals. Nevertheless, digestion with other enzymes can clearly differentiate the alpha thal1 and normal genotypes. We distinguish the findings in the alpha thalassemias from the extensive DNA polymorphism in the region of the alpha and zeta globin genes.
    Matched MeSH terms: DNA Restriction Enzymes
  11. Solvent-free lipase-catalyzed synthesis of a novel hydroxyl-fatty acid derivative of kojic acid
    El-Boulifi N, Ashari SE, Serrano M, Aracil J, Martínez M
    Enzyme Microb Technol, 2014 Feb 5;55:128-32.
    PMID: 24411455 DOI: 10.1016/j.enzmictec.2013.10.009
    The aim of this work was the synthesis of a novel hydroxyl-fatty acid derivative of kojic acid rich in kojic acid monoricinoleate (KMR) which can be widely used in the cosmetic and food industry. The synthesis of KMR was carried out by lipase-catalysed esterification of ricinoleic and kojic acids in solvent-free system. Three immobilized lipases were tested and the best KMR yields were attained with Lipozyme TL IM and Novozym 435. Since Lipozyme TL IM is the cheapest, it was selected to optimize the reaction conditions. The optimal reaction conditions were 80 °C for the temperature, 1:1 for the alcohol/acid molar ratio, 600 rpm for stirring speed and 7.8% for the catalyst concentration. Under these conditions, the reaction was scaled up in a 5×10⁻³ m³ stirred tank reactor. ¹H-¹³C HMBC-NMR showed that the primary hydroxyl group of kojic acid was regioselectively esterified. The KMR has more lipophilicity than kojic acid and showed antioxidant activity that improves the oxidation stability of biodiesel.
    Matched MeSH terms: Enzymes, Immobilized
  12. Molecular analysis of isolates of Salmonella typhi obtained from patients with fatal and nonfatal typhoid fever
    Thong KL, Passey M, Clegg A, Combs BG, Yassin RM, Pang T
    J Clin Microbiol, 1996 Apr;34(4):1029-33.
    PMID: 8815078
    Molecular characterization of a total of 52 human isolates of Salmonella typhi from Papua New Guinea was performed by using pulsed-field gel electrophoresis (PFGE) after digestion of chromosomal DNA with three restriction endonucleases, XbaI (5'-TCTAGA-3'), AvrII (5'-CCTAGG-3'), and SpeI (5'-ACTAGT-3'). Of the 52 isolates tested, 11 were obtained from patients with fatal typhoid fever and 41 were obtained from patients with nonfatal disease. The 52 isolates showed limited genetic diversity as evidenced by only three different PFGE patterns detected following digestion with XbaI (patterns X1 to X3; F [coefficient of similarity] = 0.86 to 1.0), four patterns detected following digestion with AvrII (patterns A1 to A4; F =0.78 to 1.0), and two patterns detected following digestion with SpeI (patterns S1 and S2; F = 0.97 to 1.0). Of the 52 isolates, 37 were phage typed, and all belonged to phage type D2. All 11 isolates obtained from patients with fatal typhoid fever were identical (F = 1.0) and possessed the PFGE pattern combination X1S1A1, whereas the 41 isolates from patients with nonfatal typhoid fever had various PFGE pattern combinations, the most common being X2S1A2 (39%), X1S1A1 (24%), and X1S1A2 (15%). Thus, all the isolates from patients with the fatal disease had the X1 and A1 patterns, whereas the majority of the isolates from patients with nonfatal typhoid fever possessed the X2 and A2 patterns. The data suggest that there is an association among strains of S. typhi between genotype, as assessed by PFGE patterns, and the capability to cause fatal illness. Analysis of blood and fecal isolates of S. typhi from the same patient also indicated that some genetic changes occur in vivo during the course of infection.
    Matched MeSH terms: DNA Restriction Enzymes
  13. Analysis of Salmonella typhi isolates from Southeast Asia by pulsed-field gel electrophoresis
    Thong KL, Puthucheary S, Yassin RM, Sudarmono P, Padmidewi M, Soewandojo E, et al.
    J Clin Microbiol, 1995 Jul;33(7):1938-41.
    PMID: 7665677
    Pulsed-field gel electrophoresis (PFGE) revealed that multiple genetic variants of Salmonella typhi are simultaneously present in Southeast Asia and are associated with sporadic cases of typhoid fever and occasional outbreaks. Comparative analysis of PFGE patterns also suggested that considerable genetic diversity exists among S. typhi strains and that some PFGE patterns are shared between isolates obtained from Malaysia, Indonesia, and Thailand, implying movement of these strains within these regions of Southeast Asia, where they are endemic.
    Matched MeSH terms: DNA Restriction Enzymes
  14. Fulltext Cellular Homeostasis and Antioxidant Response in Epithelial HT29 Cells on Titania Nanotube Arrays Surface
    Smn Mydin RB, Sreekantan S, Hazan R, Farid Wajidi MF, Mat I
    Oxid Med Cell Longev, 2017;2017:3708048.
    PMID: 28337249 DOI: 10.1155/2017/3708048
    Cell growth and proliferative activities on titania nanotube arrays (TNA) have raised alerts on genotoxicity risk. Present toxicogenomic approach focused on epithelial HT29 cells with TNA surface. Fledgling cell-TNA interaction has triggered G0/G1 cell cycle arrests and initiates DNA damage surveillance checkpoint, which possibly indicated the cellular stress stimuli. A profound gene regulation was observed to be involved in cellular growth and survival signals such as p53 and AKT expressions. Interestingly, the activation of redox regulator pathways (antioxidant defense) was observed through the cascade interactions of GADD45, MYC, CHECK1, and ATR genes. These mechanisms furnish to protect DNA during cellular division from an oxidative challenge, set in motion with XRRC5 and RAD50 genes for DNA damage and repair activities. The cell fate decision on TNA-nanoenvironment has been reported to possibly regulate proliferative activities via expression of p27 and BCL2 tumor suppressor proteins, cogent with SKP2 and BCL2 oncogenic proteins suppression. Findings suggested that epithelial HT29 cells on the surface of TNA may have a positive regulation via cell-homeostasis mechanisms: a careful circadian orchestration between cell proliferation, survival, and death. This nanomolecular knowledge could be beneficial for advanced medical applications such as in nanomedicine and nanotherapeutics.
    Matched MeSH terms: DNA Repair Enzymes/genetics; DNA Repair Enzymes/metabolism
  15. Fulltext Functional expression of a novel α-amylase from Antarctic psychrotolerant fungus for baking industry and its magnetic immobilization
    He L, Mao Y, Zhang L, Wang H, Alias SA, Gao B, et al.
    BMC Biotechnol, 2017 02 28;17(1):22.
    PMID: 28245836 DOI: 10.1186/s12896-017-0343-8
    BACKGROUND: α-Amylase plays a pivotal role in a broad range of industrial processes. To meet increasing demands of biocatalytic tasks, considerable efforts have been made to isolate enzymes produced by extremophiles. However, the relevant data of α-amylases from cold-adapted fungi are still insufficient. In addition, bread quality presents a particular interest due to its high consummation. Thus developing amylases to improve textural properties could combine health benefits with good sensory properties. Furthermore, iron oxide nanoparticles provide an economical and convenient method for separation of biomacromolecules. In order to maximize the catalytic efficiency of α-amylase and support further applications, a comprehensive characterization of magnetic immobilization of α-amylase is crucial and needed.

    RESULTS: A novel α-amylase (AmyA1) containing an open reading frame of 1482 bp was cloned from Antarctic psychrotolerant fungus G. pannorum and then expressed in the newly constructed Aspergillus oryzae system. The purified recombinant AmyA1 was approximate 52 kDa. AmyA1 was optimally active at pH 5.0 and 40 °C, and retained over 20% of maximal activity at 0-20 °C. The K m and V max values toward soluble starch were 2.51 mg/mL and 8.24 × 10-2 mg/(mL min) respectively, with specific activity of 12.8 × 103 U/mg. AmyA1 presented broad substrate specificity, and the main hydrolysis products were glucose, maltose, and maltotetraose. The influence of AmyA1 on the quality of bread was further investigated. The application study shows a 26% increase in specific volume, 14.5% increase in cohesiveness and 14.1% decrease in gumminess in comparison with the control. AmyA1 was immobilized on magnetic nanoparticles and characterized. The immobilized enzyme showed improved thermostability and enhanced pH tolerance under neutral conditions. Also, magnetically immobilized AmyA1 can be easily recovered and reused for maximum utilization.

    CONCLUSIONS: A novel α-amylase (AmyA1) from Antarctic psychrotolerant fungus was cloned, heterologous expression in Aspergillus oryzae, and characterized. The detailed report of the enzymatic properties of AmyA1 gives new insights into fungal cold-adapted amylase. Application study showed potential value of AmyA1 in the food and starch fields. In addition, AmyA1 was immobilized on magnetic nanoparticles and characterized. The improved stability and longer service life of AmyA1 could potentially benefit industrial applications.

    Matched MeSH terms: Enzymes, Immobilized
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