The use of the tyrosine apodecarboxylase of Streptococcus faecalis R for the estimation of codecarboxylase

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Abstract
The use of acetone-dried cells of Streptococcus faecalis R, grown in a vit. B6-free medium, as a source of tyrosine apodecarboxylase for the estimation of codecarboxylase was investigated. Satisfactory assays of codecarboxylase in animal tissues were made with such prepns., using Ca pyridoxal-5-phosphate (synthetic codecarboxylase) as standard. Sulfate, phthalate, phosphate and pyrophosphate inhibited the decarboxylation of tyrosine by acetone-dried deficient cells in the presence of small amts. of codecarboxylase. These substances did not inhibit the decarboxylation of tyrosine by intact deficient cells in the presence of pyridoxal; with acetone-dried prepns. of cells grown in a medium containing excess pyridoxal, they had little or no inhibitory effect. The action of these salts was interpreted as an interference with the reaction between codecarboxylase and the apoenzyme. Vit. B6-free intact cells of the organism did not decarboxylate tyrosine in the presence of either synthetic or natural codecarboxylase.
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