SUBSTRATE SPECIFICITIES OF BACTERIAL POLYHYDROXYALKANOATE DEPOLYMERASES AND LIPASES - BACTERIAL LIPASES HYDROLYZE POLY(OMEGA-HYDROXYALKANOATES)

The substrate specificities of extracellular lipases purified from Bac illus subtilis, Pseudomonas aeruginosa, Pseudomonas alcaligenes, Pseud omonas fluorescens, and Burkholderia cepacia (former Pseudomonas cepac ia) and of extracellular polyhydroxyalkanoate (PHA) depolymerases puri fied from Comamonas sp., Pseudomonas lemoignei, and P. fluorescens GK1 3, as well as that of an esterase purified from P. fluorescens GK13, t o various polyesters and to lipase substrates were analyzed. All lipas es and the esterase of P. fluorescens GK13 but none of the PHA depolym erases tested hydrolyzed triolein, thereby confirming a functional dif ference between lipases and PHA depolymerases. However, most lipases w ere able to hydrolyze polyesters consisting of an omega-hydroxyalkanoi c acid such as poly(6-hydroxyhexanoate) or poly(4-hydroxybutyrate). Th e dimeric ester of hydroxyhexanoate was the main product of enzymatic hydrolysis of polycaprolactone by P. aeruginosa lipase. Polyesters con taining side chains in the polymer backbone such as poly(3-hydroxybuty rate) and other poly(3-hydroxyalkanoates) were not or were only slight ly hydrolyzed by the lipases tested.