Substrate specificity and effects of water-miscible solvents on the activity and stability of extracellular lipase from Streptomyces rimosus

Substrate specificity, regioselectivity and transesterification activity of purified extracellular lipase from Streptomyces rimosus were investigated. The enzyme showed pronounced lipolytic activity toward a number of triacyl glycerols and oils of vegetable and animal origin. It hydrolyzed most effic iently medium chain length fatty acid glycerol esters (C8-C12). There was p reference for the esters of C16 and C18 unsaturated fatty acids over C16 an d C 18 saturated fatty acid esters, as well as for triacylglycerol substrat e with cis double bond (triolein) versus trans double bond (trielaidin). St reptomyces rimosus lipase hydrolyzed primary and secondary ester bonds in t riacylglycerols, (triolein and 2,3-dimereapto-1-propanol tributyrate). The lipase catalyzed the hydrolysis of poly(oxyethylene) sorbitan monoesters (T ween 20-80) with rate comparable for that determined with triacylglycerols and oils. Several water-miscible solvents enhanced the lipase activity. 1,4 -Dioxane activated the enzyme in a broad concentration range, up to 4-fold. Lipase was stable in solvent mixtures containing 50% (v/v) ethanol, 1,4-di oxane, acetonitrile or acetone. Tetrahydrofuran and N,N-dimethylformamide ( both 50%) inactivated the enzyme with t(1/2) of 5 min and t(1/2) of 2 h, re spectively. Transesterification of racemic 1-phenyl ethanol with vinyl acetate, catalyz ed by extracellular lipase from Streptomyces rimosus in n-hexane. proceeded with partial R-enantioselectivity. (C) 2001 Elsevier Science Inc. All righ ts reserved.