Mieko Iwai

The Effect of Reverse Action on Triglyceride Hydrolysis by Lipase

Reesterification of the fatty acid liberated during hydrolysis of triglyceride by lipase was studied by using four microbial lipases. The amount of esterified product (glycerides) was estimated by assaying incorporated [1-14C]oleic acid which was added to the reaction mixture in the course of triolein hydrolysis. The extent of esterification during glyceride hydrolysis differed among the four lipases. Rhizopus delemar lipase was found to esterify the most, followed by Penicillium cyclopium lipase. Lipases from Aspergillus niger and Geotrichum candidum did not show marked esterifying activity during hydrolysis of glycerides. Synthesis of monoolein from hydrolysis products (glycerol and oleic acid) was not observed for any lipase used in reaction mixtures for triolein hydrolysis. The esterifying activity that was observed during hydrolysis of triglyceride is considered to be one of the main Causes for diversity in the time course of triglyceride hydrolysis by the four lipases.

Crystallographic data and circular dichroism spectrum of lipase from Geotrichum candidum link.

Single crystals of lipase from Geotrichum candidum Link have been obtained for a high resolution structural analysis. The crystals are monoclinic, space group P2 1 , with unit cell dimensions of a =59·3 A, b =83·8 A, c =55·7 A, β=100·1 o . An asymmetric unit contains one protein molecule.

Purification and some Properties of the Lytic Enzyme from Bacillus R-4 which Acts on Rhizopus Cell Wall

A lytic activity on cell wall of Rhizopus species which was shown by culture filtrate of Bacillus R–4 was separated into two fractions (Fraction I and II) with the lytic activity by means of SP-Sephadex column chromatography.The lytic activity of the Fraction II was twice as strong as that of the Fraction I and the lytic action pattern on Rhizopus cell wall of the mixture of these fractions was similar to that of the crude enzyme preparation.The Fraction I was recognized as a kind of proteolytic enzyme and was purified as a ultracentrifugally and electrophoretically homogeneous preparation.On the other hand, the Fraction II was a kind of carbohydrolase which acted on glycol chitosan and liberated hexosamine from Rhizopus cell wall accompanying the lysis.