NCIt definition : A non-metabolizable synthetic amino acid, formed through the cyclization of the amino
acid leucine, with immunosuppressive, antineoplastic, and cytostatic activities. Cycloleucine
competitively inhibits the enzyme methionine adenosyltransferase, resulting in the
inhibition of S-adenosylmethionine (SAM) synthesis from methionine and ATP, and subsequent
nucleic acid methylation and polyamine production; RNA, and perhaps to a lesser extent,
DNA biosyntheses and cell cycle progression are finally disrupted. This agent is also
a competitive inhibitor at the glycine modulatory site of the N-methyl-D-aspartate
(NMDA) receptor.;