In the present experiments the action of carboxypeptidase on chloracetyl, α-bromo-propionyl and α-bromo-isocapronyl derivatives of o-, m- and p-aminobenzoic acids was examined at a different pH value of the medium.
1. Of all the substrates tested olily m- and p-aminobenzoic acids derivatives are hydrolyzed by carboxypeptidase, m-compounds being always more readily attacked than p-compounds. o-amino-benzoic acid compounds are, however, found to be quite resistant to the enzyme.
2. The optimum pH for the action on m- and p-compounds lies at 8.4.
3. α-bromo-propionyl derivatives are most rapidly split by carboxypeptidase. Chloracetyl compounds are hydrolyzed at a lower rate than α-bromo-propionyl compounds, but more quickly than α-bromo-isocapronyl derivatives.
4. o-, m- and p-aminobenzoic acids exert a similar inhibitory effect on carboxypeptidase. Monochloraeetic acid also inhibits the activity of carboxypeptidase.
5. There exist no relations between the rate of alkali hydrolysis of these aminobenzoic acid compounds and their cleavability by means of carboxypeptidase.
In conclusion the author wishes to express his sincere thanks to Prof. Dr. T. Uchino for his kind direction throughout this work.
The expence of this research was defrayed from the Scientific Expenditure of the Department of Education. T. Uchino.
