Thiol-subtilisin, in which a serine side chain at the active site was replaced by a cysteine residue, was orepared from chromatographically purified subtilisin. The thidl derivative was separated from native subtilisin by ion-exchange chromatography. The unexpectedly marked difference in Chromatographie behavior indices an alteration in some of the physical properties of the protein molecule. Pure thiol-subtilisin exhibits a very low activity toward p-nitrophenyl N-benzyloxycarbonylglycinate which is a specific substrate for subtilisin. This low activity is interpreted in terms of a distortion of the active site of the thiol-enzyme rather than in terms of a difference in chemical reactivity between hydroxyl and sulfhydryl groups.
|Number of pages||6|
|Publication status||Published - 1969|
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