Enzymes accompanying tyrosine phenol lyase and the problem of its substrate specificity

The cells ofEscherichia intermedia A-21, known as a producer of tyrosine phenol lyase, are shown to produce D-serine dehydratase, L-serine dehydratase, and alanine racemase. Since the specific activities of the latter by far exceed that of tyrosine phenol lyase, minor concentrations of these independent enzymes in purified preparations of tyrosine phenol lyase may cause the observed levels of side activities with respect to serine and alanine. In the light of the results obtained, the assumption of the polysubstrate nature of tyrosine phenol lyase seems insufficiently substantiated.