engleski

Bioinformatic analysis of lipases from bacteria of genus Streptomyces

Lipases (triaclyglycerol acylhydrolases, EC 3.1.1.3) catalyse hydrolysis and synthesis of lipids, depending on the reaction conditions. The ability of these enzymes to stereospecifically catalyse various reactions on a broad range of substrates gives them significant biotechnological potential. Streptomycetes are Gram-positive soil bacteria that exhibit remarkable capacity for synthesis of secondary metabolites. Although best known as antibiotics producers, they also produce and secrete various hydrolytic enzymes. However, among streptomycetes, genes of five lipases are cloned and sequenced, only. The available structural data on streptomycete lipases are very limited. However, there are their protein sequences deposited in data bases. Therefore, analysis of these sequences was performed by bioinformatics methods to obtain some data on structure and function of streptomycete lipases. According to available biochemical data and sequence analysis, lipases from bacteria of genus Streptomyces were classified into three groups that differ substantially. Lipases from S. exfoliatus, S. coelicolor and S. albus G have revealed high sequence homology. They are typical lipases containing Ser-His-Asp catalytic triad with Ser in the conserved GXSXG pentapeptide. They have two cysteines bound covalently. Unlike most of other lipases, they do not posses a lid that covers active site in water environment. Although these enzymes are structurally very similar, differences among them exist, primarily regarding protein hydrophobicity and stability. Lipase from S. cinnamomeus reveals characteristics typical of lipases. It belongs to Pseudomonas family of bacterial lipolytic enzymes and probably possesses a lid. It is predicted to be rather stable. Lipase from S. rimosus belongs to family of GDSL-hydrolases that comprises mostly esterases. This enzyme has Ser of catalytic triad in GDS(L) motif instead of characteristic GXSXG pentapeptide. It has three disulfide bridges that probably contribute to observed thermal stability of this enzyme. Topology of secondary structure elements and active site residues of S. rimosus lipase differs significantly from classical lipases ; it exhibits a novel protein fold, being different from the canonical α /b fold.

lipases; Streptomyces; bioinformatics

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