Protein carboxyl methylation in the mushroom Volvariella volvacea

Abstract

The mushroom, Volvariella volvacea, when grown under shake-flask conditions, produced protein carboxyl-methyl transferase intracellularly. Relatively high amounts of enzymic activity were produced on the first day of growth, which decreased to almost half of the initial level from the second day onwards. The temperature and pH optimum for the enzyme were 50° and 6, respectively. The Michaelis—Menten constant ( K m ) for S-adenosyl- l-methionine was 2μM. S-Adenosyl- l-homocysteine appeared to be a competitive inhibitor, its K i being 2.5μM. Enzymic and/or non-enzymic hydrolysis of methylated protein was observed even at pH 6. From these observations the existence of a second class of protein carboxyl-methyl transferase was suggested.