The zinc ion is a biologically essential elements. It often constitutes active centers of hydrolytic zinc enzymes. Metalloproteases which contain zinc atoms are very important enzymes in food, pharmaceutical and fermentation industries, therefore many zinc proteases have been isolated and characterized. But most of investigations have centered around the molecular masses from 28,000 to 57,000 Da and little is known about small neutral proteases. In this report, we have studied the structure and function of a small zinc protease from Streptomyces caespitosus. It was the smallest zinc protease which hydrolyzed highly specificically and its crystal structure was revealed at 1.6 A resolution. Now, atomic resolution structure analysis is in progress.

current address
* Institute for Protein Research, Osaka University, Suita, Osaka 565, Japan
** Faculty of Pharmaceutical Sciences, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan