title: Molecular cloning, expression and biochemical characterisation of a cold-adapted novel recombinant chitinase from Glaciozyma antarctica PI12.
abstract: BACKGROUND
  Cold-adapted enzymes are proteins produced by psychrophilic organisms that display a high catalytic efficiency at extremely low temperatures. Chitin consists of the insoluble homopolysaccharide β-(1, 4)-linked N-acetylglucosamine, which is the second most abundant biopolymer found in nature. Chitinases (EC 3.2.1.14) play an important role in chitin recycling in nature. Biodegradation of chitin by the action of cold-adapted chitinases offers significant advantages in industrial applications such as the treatment of chitin-rich waste at low temperatures, the biocontrol of phytopathogens in cold environments and the biocontrol of microbial spoilage of refrigerated food.
  
  
  RESULTS
  A gene encoding a cold-adapted chitinase (CHI II) from Glaciozyma antarctica PI12 was isolated using Rapid Amplification of cDNA Ends (RACE) and RT-PCR techniques. The isolated gene was successfully expressed in the Pichia pastoris expression system. Analysis of the nucleotide sequence revealed the presence of an open reading frame of 1,215 bp, which encodes a 404 amino acid protein. The recombinant chitinase was secreted into the medium when induced with 1% methanol in BMMY medium at 25°C. The purified recombinant chitinase exhibited two bands, corresponding to the non-glycosylated and glycosylated proteins, by SDS-PAGE with molecular masses of approximately 39 and 50 kDa, respectively. The enzyme displayed an acidic pH characteristic with an optimum pH at 4.0 and an optimum temperature at 15°C. The enzyme was stable between pH 3.0-4.5 and was able to retain its activity from 5 to 25°C. The presence of K+, Mn2+ and Co2+ ions increased the enzyme activity up to 20%. Analysis of the insoluble substrates showed that the purified recombinant chitinase had a strong affinity towards colloidal chitin and little effect on glycol chitosan. CHI II recombinant chitinase exhibited higher Vmax and Kcat values toward colloidal chitin than other substrates at low temperatures.
  
  
  CONCLUSIONS
  By taking advantage of its high activity at low temperatures and its acidic pH optimum, this recombinant chitinase will be valuable in various biotechnological applications under low temperature and acidic pH conditions.
authors: Department of Bioprocess Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, Skudai, Johor, Malaysia.
authors: Aizi Nor Mazila
authors: AN
authors: Ramli
authors: Nor Muhammad
authors: NM
authors: Mahadi
authors: Amir
authors: A
authors: Rabu
authors: Abdul Munir Abdul
authors: AM
authors: Murad
authors: Farah Diba Abu
authors: FD
authors: Bakar
authors: Rosli Md
authors: RM
authors: Illias
mesh_terms: D000595:Amino Acid Sequence; D001487:Basidiomycota / Q000737:chemistry / Q000145:classification / Q000201:enzymology* / Q000235:genetics; D002688:Chitinases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D003080:Cold Temperature; D004795:Enzyme Stability; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D007700:Kinetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D010843:Pichia / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D013379:Substrate Specificity
chemical_list: D005656:Fungal Proteins; D011994:Recombinant Proteins; D002688:Chitinases