Survey methodology and objectives: A traditional review approach was taken to focus on the engineering of microbial -amylases to enhance industrially favoured characteristics. The action mechanisms of - and -amylases were compared to avoid any bias in the research background. This review aimed to discuss the advances in modifying microbial -amylases via protein engineering to achieve longer half-life in high temperature, improved resistance (acidic, alkaline and oxidative) and enhanced specificities (substrate and product). Captivating results were discussed in depth, including the extended half-life at 100C, pH 3.5 and 10, 1.8 M hydrogen peroxide as well as enhanced substrate (65.3%) and product (42.4%) specificities. These shed light to the future microbial -amylase engineering in achieving paramount biochemical traits ameliorations to apt in the industries.
Conclusions: Microbial -amylases can be tailored for specific industrial applications through protein engineering (rational design and directed evolution). While the critical mutation points are dependent on respective enzymes, formation of disulfide bridge between cysteine residues after mutations is crucial for elevated thermostability. Amino acids conversion to basic residues was reported for enhanced acidic resistance while hydrophobic interaction resulted from mutated hydrophobic residues in carbohydrate-binding module or surface-binding sites is pivotal for improved substrate specificity. Substitution of oxidation-prone methionine residues with non-polar residues increases the enzyme oxidative stability. Hence, this review provides conceptual advances for the future microbial -amylases designs to exhibit industrially significant characteristics. However, more attention is needed to enhance substrate specificity and oxidative stability since they are least reported.
Objectives: In this study, we aimed to report the complete nucleotide sequence of Malaysian isolate of Rice tungro spherical virus Seberang Perai (RTSV-SP) for the first time. RTSV-SP was characterized and its evolutionary relationship with previously reported Indian and Philippines isolates were elucidated.
Materials and Methods: RTSV-SP isolate was isolated from a recent outbreak in a paddy field in Seberang Perai zone of Malaysia. Its complete genome was amplified by RT-PCR, cloned and sequenced.
Results: Sequence analysis indicated that the genome of RTSV-SP consisted of 12,173 nucleotides (nt). Comparative analysis of 6 complete genome sequences using Clustal Omega showed that Seberang Perai isolate shared the highest nucleotide identity (96.04%) with Philippine-A isolate, except that the sORF-2 of RTSV-SP is shorter than RTSV Philippine-A by 27 amino acid residues. RTSV-SP found to cluster in Southeast Asia (SEA) group based on the whole genome sequence phylogenetic analysis using MEGA X software.
Conclusions: Phylogenetic classification of RTSV isolates based on the complete nucleotide sequences showed more distinctive clustering pattern with the addition of RTSV-SP whole genome to the available isolates. Present study described the isolation and molecular characterization of RTSV-SP.