The substrate specificity of the tyrosine decarboxylase of Streptococcus faecalis

Abstract

Acetone-driedl prepns. of S. faecalis R decarboxylated m-hydroxyphenylalanine at about 30% of the rate at which they decarboxylated tyrosine. The reaction appeared to be specific for the L m-hydroxyphenylalanine, which was decarboxylated quantitatively to m-hydroxyphenylethylamine. Washed suspensions of intact resting cells of the organism had no detectable action on m-hydroxyphenylalanine. Dried prepns. of S. faecalis R did not decarboxylate o-hydroxyphenylalanine at a significant rate, nor had this amino acid any detectable affinity for tyrosine decarboxylase. Neither dried prepns. nor intact cells of S. faecalis R had any significant action on 2,5-dihydroxy-phenylalanine.