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Articles

Metalloenzyme Inhibitor from Kidney Beans

Partial Purification and Characterization ¹

Clarence A. Ryan^b,2

^a Faculty of Pharmaceutical Sciences, Science University of Tokyo, Shinjuku-ku, Tokyo 162, Japan, Department of Agricultural Chemistry, and Program in Biochemistry and Biophysics, Washington State University, Pullman, Washington 99164

Inhibitory activity directed against metalloenzymes has been highly purified from extracts of red kidney beans (Phaseolus vulgaris). The inhibitor is a substance of small molecular weight and appears to be a chelator of Zn²⁺. One milligram of the preparation inhibited 23 milligrams carboxypeptidase A. The inhibitor also strongly inhibited carboxypeptidase B and alkaline phosphatase and could activate phosphoglucomutase that had previously been inactivated with Zn²⁺. The isoelectric point of the inhibitor is 4.7. The inhibitor activity was abolished by preincubation with Zn²⁺, Ni²⁺, Co²⁺, or Cu²⁺. The mechanism of inhibition of carboxypeptidases and alkaline phosphatase by the bean inhibitor is apparently due to the complexing and complete removal of Zn²⁺ from the enzymes.

¹ Scientific Paper No. 5204, Project 1791, College of Agriculture Research Center, Washington State University. This study was supported in part by grants from the Ministry of Education, Science and Culture of Japan, and from the Naito Foundation (Code No. 72-410).