engleski

Protein sequence analysis of Streptomyces rimosus extracellular lipase

Lipases (triacylglycerol acylhydrolases, EC 3.1.1.3) catalyse hydrolysis and synthesis of lipids, depending on the reaction conditions. Their natural substrates are insoluble in water; therefore hydrolysis takes place on lipid-water interface. This property distinguishes lipases from classical esterases. 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 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, not much is known about their lipolytic enzymes. We have previously reported purification and biochemical characterisation of the native extracellular lipase from Streptomyces rimosus. Here are presented cloning and protein sequence analysis of this enzyme. A lipase gene from S. rimosus was cloned using the data provided by amino acid sequencing. The gene was sequenced and amino acid sequence was deduced. S. rimosus lipase consists of 268 amino acid residues, of which 34 presumably belong to signal peptide. The cleavage site has been determined by N-terminal sequencing of the mature lipase. Although this enzyme was shown to be a true lipase, belonging to family II of lipolytic enzymes, it showed no overall amino acid sequence similarity to other lipases in databases. Closest related sequences were those of the two Streptomyces coelicolor A3(2) putative hydrolases. Similarity was also found with the Streptomyces scabies esterase, which is the only member of family II of lipolytic enzymes with solved three-dimensional structure. Secondary structure prediction was performed for the S. rimosus lipase by various methods; consensus prediction was determined and compared to secondary structure of the S. scabies esterase. High degree of agreement between these structures suggests that the S. rimosus lipase might have three-dimensional structure different from other lipases.

Streptomyces rimosus; lipase; protein sequence analysis

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