On the unity of castor lipase.

Abstract

The peculiar activation of castor bean lipase by acids and the changes that this lipase undergoes during germination have attracted the interest of investigators for a long time. The contradictory views on the nature of the activation of castor lipase by acids are partly due to the different character of the two kinds of castor lipase preparations commonly used. Castor lipase in the form of “lipase cream” is in no way altered by water, while the lipase preparation known as “defatted seed” is easily destroyed by it.

In our experiments lipase cream and defatted seed were prepared according to Willstätter and Waldschmidt-Leitz 1 ; the lipase estimations were carried out as described by Willstätter, 2 olive oil being used as substrate.

When prepared from resting seed, lipase cream and defatted seed both show that castor lipase has an exceptionally sharp pH optimum around pH 4.7 and no activity in a neutral medium; the lipase is not injured by dilute alkali and its synthesizing power is practically nil. If we, however, subject lipase cream to a treatment with aqueous reagents of a pH of 4.7 (dilute HCN, acetate buffer, citrate buffer), it becomes evident that we are dealing now with a lipase which has properties quite different from what they were before such treatment. The former sharp pH optimum at pH 4.7 has disappeared, and castor lipase is now more uniformly active over a much wider range of the pH and active even in a neutral medium. Further, castor lipase thus treated has become easily destructible by dilute alkali and gained considerable synthetic power. It is important to lay stress upon our finding that the characteristic alterations of lipase cream by aqueous reagents of pH 4.7 take place, while the total lipolytic activity is fully preservecl∗