engleski

Substrate specificity and regioselectivity of extracellular lipase from Streptomyces rimosus.

Lipases are enzymes capable to hidrolyze ester bonds of fatty acid triglycerols. Their characteristic is interfacial activation i.e. marked increase of catalytic power upon contact with emulsified substrates. Although defined as triacylglicerol acylhydrolases (E.C. 3.1.1.3), they can hidrolyze other esters and catalyze various reactions of esterification. This makes them important biocatalysts applicable in organic chemistry, pharmaceutical industry and biotechnology. We have previously reported purification and partial characterization of extracellular lipase from Streptomyces rimosus. The object of this study was its substrate and positional specificity (regioselectivity). The acyl-chain length specificity was examined with p-nitrophenyl esters and glycerol esters of various fatty acids. The preference for esters of medium size fatty acids was found in both cases. Interfacial activation was demonstrated with p-nitrophenyl butyrate as substrate. Positional specificity was determined with alpha and beta-naphthyl esters, triolein and 2,3-dimercapto-1-propanol tributyrate. The reactions were followed spectrophotometrically or by thin layer chromatography. It was revealed that S. rimosus extracellular lipase cleaves equally well ester bonds at position 1 and 2 of the examined substrates. Thus, like majority of bacterial lipases, it belongs to the group of positionally nonspecific lipases.

Streptomyces rimosus; lipase; substrate specificity; positional specificity; interfacial activation

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