p-Cresol formation by cell-free extracts of Clostridium difficile

Cell-free extracts of Clostridium difficile were shown to form p-cresol by decarboxylation of p-hydroxyphenylacetic acid. This activity required both high and low molecular weight fractions. The active component of the low molecular weight fraction had properties of an amino acid and could be replaced by serine, threonine or the corresponding alpha keto acids. Pyruvate was shown to function catalytically. Since the high molecular weight fraction was O2-sensitive and since dithionite was as effective as pyruvate with some high molecular weight fractions, the alpha keto acids probably serve as low potential reducing agents in this system. Because of instability, the p-cresol-forming enzyme could not be purified.