SYN: proenzyme.
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zy·mo·gen 'zī-mə-jən n an inactive protein precursor of an enzyme secreted by living cells and converted (as by a kinase or an acid) into an active form called also proenzyme
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n.
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zy·mo·gen (ziґmo-jən) a proenzyme, particularly of a proteolytic enzyme.Medical dictionary. 2011.