Acid phosphatase of the prostate gland. II. Factors influencing enzymatic activity; structural characteristics

Abstract

Maximum activities are obtained with substrates of a phenolic nature and phosphoric esters of heterocycles. Average  activities appear with ribose phosphoric monoesters and those derived from tricarbonate hydroxylates. There is no ac­tivity with phosphoric diesters, pyrophosphoric compounds. hexose esters or with labile phosphates.

Both fractions I and II retain maxi­mum activity for a practically unlimited period of time when they are kept in a liophylised form. In an aqueous solution they retain their activity at —8 and 0 for at least 7 days. while at 4 a decline is noted after 24 hours; at 25 and 37 this decline is evident after 1 hour.

We have found an activation energy of 7.590 calories/mole for fraction I, and of 5.120 for fraction II.

We have found a strong inhibition of acid phosphatase I by the ions Mg2+ and Ni2+. and somewhat less by Ca2+, Zn2+ and Co2+. As regards phosphatase II we have only found an average inhibition by the ion Ni2+, the others being inactive.

The conclusión is drawn that they are not metaloenzymes, at least with a dialysable metallic component.

Fluorides and l-threo-(+)-tartaric acid strongly inhibit both fractions I and II; a somewhat less inhibition is produced by the oxalates. The inhibition which appears in both enzymes with p-CI-mercuryben-zoate, quite apparent, disappears when thvolic compounds (cysteine, glutation or BAL) are added to the incubation mix­ ture, at a concentraron equal to that of the inhibitor. Of all these, the most effective, as an anti-inhibitor, is BAL.

For fractions I and H we have obtained molecular wcights of 120,000 and 85,000 respectively. The study of the constituen amino acids indicates that the majority are: histidine, glutamic acid, alanine, serine and aspartic acid; the quantity of cysteine is also appreciable, which cor­ robórales the fundamental character of this enzyme so that the hydrolytic capacity is maintained. Glycine undergoes a negative change of 72 % from fraction I to fraction II.