Isolation of a tyrosine-activating enzyme from baker's yeast

Abstract

The extracts of ether-CO2-frozen baker's yeast contain enzymes that catalyze the ATP-linked amino acid activation by way of pyrophosphate elimination. From the extract a tyrosine-activating enzyme could be isolated, which, judging from ultracentrifugation and electrophoretic data, was about 70% pure at the final stage of the isolation procedure. The enzymic activity is measured by tyrosine-specific hydroxamate formation as well as by tyrosine-linked ATP-pyrophosphate exchange. The enzyme proved to be substrate-specific.