Aspects of the biosynthesis of carolic and carlosic acids in Penicillium charlesii: A 13CNMR study.
1980
Reffstrup T. | Boll P.M.
The origin of two metabolic products of Penicillium charlesii NRRL 1887, carolic and carlosic acids has been reinvestigated in a ('13)C labelling study. The main biosynthetic pathway was established to be the combination of a C(,6) polyketide unit with a C(,4) compound closely related to succinic acid in agreement with earlier findings. Repeated experiments showed that a bilateral mixing of intact acetate units occurred between the acetate pool and the incorporated C(,4) unit. Dehydrocarolic acid could be converted to carolic acid in a cell free extract of P. charlesii, whereas an earlier proposal of carlosic acid as a precursor of carolic acid could not be confirmed. A new biosynthetic scheme is proposed considering oxalacetate as the actual C(,4)-precursor. On reaction with a Beta-ketocaproyl moiety the formed alpha-(alpha-ketosuccinyl)-Beta-ketocaproate is considered the key intermediate in the biosynthesis of the 3-acyltetronic acids of the 5-methyl series as well as of the 5-carboxymethyl series. The occurrence of viridicatic acid as a metabolite of P. charlesii was established.
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