A strain of Clauiceps purpurea, which has consistently failed to elaborate ergot alkaloids when growing as a parasite, has been shown to perform only the first step of the ergoline biosynthetic pathway catalysed by dimethylallyltryptophan (DMAT) synthetase. The next step, involving Nmethylation of DMAT, did not operate.[ 14C]Agroclavine and lysergic acid, normally intermediates in alkaloid biosynthesis, were accepted by parasitic sclerotial tissue as substrates and were metabolized to lysergic acid amide (LAA). This amide therefore constituted a previously unreported end product for C. purpurea. It is concluded that the mutant has a metabolic block in the pathway following DMAT and, while enzymes for several subsequent steps are present, the fungus seems unable to form the usual cyclic tripeptide ergot alkaloids. The steps involved in metabolizing agroclavine to LAA were insensitive to 1 M-phosphate, while this concentration of phosphate completely inhibited DMAT synthetase. This double mutant therefore has unique potential for exploring control mechanisms in ergot alkaloid biosynthesis.
1257Carnosine-synthetase activity has been shown to be present in chick erythrocytesS; however, no synthetase activity was detected in rabbit reticulocytes or erythrocytes under our conditions. It may be that the enzyme lost activity prior to the time of assay, since there is a loss in enzyme activity from rat skeletal muscle shipped in this manner. It was interesting to find higher carnosine levels in rabbit reticulocytes than in rabbit erythrocytes. Mammalian reti-culocytes differ from mammalian erythrocytes in many respects s'9. Reticulocytes have the ability to synthesize globin, whereas mature erythrocytes have lost all of their ability to synthesize proteing-~k It may be that carnosine is somehow involved in RNA and/or protein synthesis in reticulocytes. Studies with inhibitors of carnosine synthesis may be useful in elucidating the physiological function of carnosine in mammalian reticulocytes.
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