engleski

The third lipolytic-family in Streptomyces, represented by the novel GDS(L) lipase from S. rimosus

The use of enzymes as biodegradable and stereospecific catalists has been increasing significantly. Seventy five percent of the enzymes of industrial interest are hydrolases. After proteases and carbohydrases, lipases (E.C.3.1.1.3) have the third largest sales volume. Microbial lipases are widely diversified in their enzymatic properties and substrate specificities, and are generally more stable than animal or plant lipases. Besides, the availability of large quantity of microbial enzymes obtained by fermentation has broadened the search for potential industrial uses of bacterial and fungal lipases. The genus Streptomyces consists of sporulating Gram-positive soil bacteria with a mycelial growth habit and a life cycle with complex morphological and physiological differentiation. According to the previously published results it seems that members of this genus are not typical lipase producers compared to other bacteria. There are only five cloned and sequenced lipase genes from streptomycetes described so far. We have previously purified to homogeneity and described the biochemical properties of an extracellular lipase from Streptomyces rimosus R6-554W. This Streptomyces lipase might have significant biotechnological potential due to its relatively high working temperature, pronounced stability as well as an unchanged activity over a broad pH range. The analysis of recently cloned lipase gene and deduced amino acid sequence revealed that this novel extracellular lipase from S. rimosus is different from the other streptomycetes lipases. There are only three isolated lipases from: S. exfoliatus, S. albus and S. coelicolor exhibiting more than 80 % sequence identity in spite of their taxonomic divergence. On the other hand lipase produced by S. cinnamomeus shows no similarity to either S. rimosus lipase or to the other three lipases. Therefore, it appears that there is much higher heterogeneity among lipases produced by Streptomyces than expected. Bacterial lipases and esterases are classified according to their conserved sequence motifs and biological properties into eight major families. Based on this classification S. cinnamomeus lipase belongs to family I while S. exfoliatus, S. albus and S. coelicolor A3(2) lipases are members of family III. Our results show that the novel S. rimosus lipase as well as 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 unrecognized in Streptomyces. To our knowledge, there is only one bacterial lipase characterized from Photorabdus luminescens that belongs to the same family of lipolytic enzymes. Analysis performed by CLUSTALX program did not show significant homology of these two GDS(L) lipases.

GDS(L) lipolytic enzymes; Streptomyces lipase; Streptomyces rimosus; Gram-positive bacteria

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