DNase II in Spermatozoa of the Loach Misgurnus fossilis L.

Yu. V. Nechaevsky^1* and V. A. Ivanov²

¹Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142292 Russia; fax: (27) 79-0553

²Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, Pushchino, Moscow Region, 142292 Russia; fax: (095) 923-3602; E-mail: ivanov@ibpm.serpukhov.su

^* To whom correspondence should be addressed.

Received October 19, 1998; Revision received February 11, 1999

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A deoxyribonuclease (DNase) which is active at acid pH in the absence of bivalent cations was found in loach spermatozoa. The enzyme was purified by ion-exchange chromatography and partially characterized. The DNase has optimal activity at pH 5.5 and its molecular weight is about 30 kD; its substrate is covalently closed circular duplex DNA, and its product is the corresponding unit-length linear DNA. The DNase is inhibited by MgCl₂ and activated by EDTA. Thus, this endoDNase found in loach spermatozoa can be classified as a DNase II. The biological role of this DNase II is discussed.

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KEY WORDS: loach spermatozoa, acid DNase, chromatographic purification, enzyme properties

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