REACTION OF FORMALDEHYDE AND THIOFORMALDEHYDE WITH MERCURIPAPAIN

Abstract

In a colorimetric assay with benzoyl-DL-arginine p-nitroanilide, acetylated and benzoylated papains retain full activity. Thus the ε-amino groups of the lysine residues are not required for enzyme activity. Intramolecular crosslinking of an enzyme could in theory stabilize secondary and tertiary structure and oppose denaturation. Thioformaldehyde is much more reactive with mercuripapain than formaldehyde, incorporating much more readily into the enzyme at equivalent concentrations. Incorporation is extensive, however, on reactive functional groups on the amino acid side chains, since acetylation decreased the incorporation markedly. In no case was there evidence of heat stabilization.