Lipase from Pseudomonas fragi. I. Purification of the Enzyme

Purification and properties of a glycerol ester hydrolase (lipase) from Propionibacterium shermanii

An intracellular glycerol ester hydrolase (lipase) from Propionibacterium shermanii was recovered from cell-free extracts and purified by ammonium sulfate precipitation, gel filtration, and ion-exchange chromatography on diethylaminoethylcellulose. Maximum enzyme activity was observed at pH 7.2 and 47 C when an emulsion of tributyrin was used as substrate. The enzyme was stable between pH 5.5 and 8. Heating the enzyme solution at 45 C for 10 min resulted in a 75% decrease in activity. Maximum rate of hydrolysis of triglycerides was observed on tripropionin, followed in order by tributyrin, tricaproin, and tricaprylin. The lipase was strongly inhibited by mercury and arsenicals, but specific sulfhydryl reagents had little or no inhibiting effect on the enzyme activity. The enzyme also showed some esterase activity, but the hydrolysis of substrates in solution was small as compared to the hydrolysis of substrates in emulsion.

Lipase from Pseudomonas fragi. II. Properties of the Enzyme

The optimal pH value of a lipase from Pseudomonas fragi was between 7.5 and 8.9, and a high reaction rate was observed at 54 C. Heating the enzyme solution at 63 C for 30 min inactivated only 27.6% of its activity; however, total inactivation was observed at 66 C after 1 hr and at 71 C after 10 min. The lipase was inhibited strongly by Fe and Fe ions, and to a lesser extent by Co, Cu, Zn. No inhibition was observed with Ca or NaF. Ethylenediaminetetraacetate was effective in removing the toxicity of Fe. The activity of the enzyme was inhibited markedly by p-chloromercurobenzoate, but the effects of N-ethylmaleimide and iodoacetate were moderate. The enzyme was able to hydrolyze natural fats, synthetic triglycerides, and alcohol esters. The order of the rate of hydrolysis of some triglycerides under experimental conditions was, from the fastest to the lowest, trilaurin, tricaprin, tricaprylin, tripalmitin, tributyrin, tricaproin, and tristearin. The enzyme was capable of hydrolyzing methyl butyrate, but the rate of hydrolysis was about one-fifth that for triolein and one-thirteenth that for coconut oil. The enzyme lost its activity rapidly when held frozen, at 20 C, and at the extremes in pH. Glutathione, cysteine, and mercaptoethanol did not preserve the activity of the enzyme.