L-Threonine deaminase as a possible antitumor agent.

In vitro studies with L-threonine deaminase purified from sheep liver demonstrated that the enzyme was cytotoxic toward two lines of murine leukemia cells but not toward L cells or normal human fibroblasts. When L-threonine deaminase was injected into mice, it was possible to lower the plasma L-threonine concentration by 90%. The enzyme had a half-life of 1.5 hours in the circulation.