engleski

A novel type of extracellular lipase from Streptomyces rimosus: isolation, (bio)chemical characterisation, cloning and crystallisation

The genus Streptomyces involves sporulating Gram-positive soil bacteria of a mycelial growth habit and a life cycle of complex morphological and physiological differentiation. The members of this genus are not typical lipase producers comparing to other bacteria. An extracellular lipase was isolated from cell filtrate by column chromatography using CM-cellulose, rechromatography, gel filtration, and FPLC monoQ. An enzyme is monomeric, basic protein of Mr =27.5 kDa, PI = 8.45, active toward triolein and p-nitrophenylesters with preference for those of C8-C12 acyl chain length. Interfacial activation was observed with p-nitrophenyl butyrate as substrate; the lipase reveals the highest activity at 50-60˚ C and at pH 9-10 and it is stable at a broad pH range of 4-10. Dithiothreitol moderately inactivates the enzyme. The isolated enzyme might have biotechnological potential due to its relatively high working temperature, pronounced stability and activity over a broad pH range. A lipase gene from Streptomyces rimosus was cloned and sequenced: 268 amino acid residues, including 34 of the signal peptide. There are three lipases isolated from: S. exfoliatus, S. albus, and S. coelicolor revealing more than 80% sequence identity in spite of their taxonomic divergence. However, lipase produced by S. cinnamomeus shows no similarity to neither S. rimosus lipase nor to the other three lipases. It appears that there is pronounced heterogeneity among lipases produced by Streptomyces than expected. The novel S. rimosus lipase and the S. coelicolor putative hydrolases that were found by data base search belong to GDS(L) or family II of the lipolytic enzymes, thus representing a third lipase family previously unrecognised in Streptomyces. To our knowledge, there is a lipase from Photorabdus luminescens belonging to this family of lipolityc enzymes. Analysis performed by CLUSTALX program did not show significant homology of these two GDS(L) lipases.

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