Activities of some Enzymes Involved in Metabolism of Carbohydrate during Sporophore Development in Coprinus cinereus

Abstract

Measurements of the specific activities of representative enzymes of the pentose phosphate cycle, Embden-Meyerhof-Parnas (EMP) pathway and the tricarboxylic acid (TCA) cycle in Coprinus cinereus sporophores at different stages of development indicate that glycolysis is the major route of carbohydrate catabolism throughout sporophore development. Enzymes of the pentose phosphate cycle were always at lower specific activities than the enzymes of the EMP pathway, and the activities of the pentose phosphate cycle enzymes declined drastically as development proceeded. This conflicts with the findings for Agaricus bisporus, but the changes in some enzymes were qualitatively similar to those occurring in the development of sporophores of Schizophyhm commune. A number of enzymes of the TCA cycle were detected, but there was no 2-oxoglutarate dehydrogenase activity nor increase of isocitrate lyase activity over the basal repressed leve!. However, glutamate decarboxylase and 4-aminobutyrate aminotransferase were detected, suggesting that the inoperative a-oxoglutarate dehydrogenase is by-passed through the glutamate decarboxylation loop. The results are discussed in relation to the changes which also occur in the specific activities of the two glutamate dehydrogenase enzymes during development of the sporophore.

Co-ordinate Regulation of Enzymes Involved in Ornithine Metabolism and its Relation to Sporophore Morphogenesis in Coprinus cinereus

“…After 1 h incubation with [14C]glutamate, 22 % of the radioactivity recovered from cap tissue appeared as 4-aminobutyrateY and 54 % as malate, succinate and citrate; the corresponding figures for experiments with stipe tissue were 38 % and 35 %, respectively. These results amply confirm the suggestion made on the basis of enzymological data that the Krebs cycle in Coprinus proceeds via the glutamate decarboxylation loop (Moore & Ewaze, 1976). It is significant that some of the isotopic label added in the form of glutamate was recovered as arginine, and that more arginine was labelled by the cap tissue (6 % of the recovered radioactivity) than by stipe tissue (2 %).…”

“…Young mycelium was harvested and assayed after 3 d incubation at 37 "C in the dark. Old mycelium was incubated for a further 5 to 7 d in the illumination conditions described by Moore & Ewaze (1976); it was harvested when sporophore primordia appeared, but these were removed and discarded before the mycelium was homogenized.…”

“…The function of the enzyme is also obscure, particularly as high activities of a NAD-linked glutamate dehydrogenase can be demonstrated in both cap and stipe. Involvement of glutamate dehydrogenase activity in a central part of carbon metabolism is implied by the observation that an inoperative 2-oxoglutarate dehydrogenase in the tricarboxylic acid cycle is by-passed through the glutamate decarboxylation loop (Moore & Ewaze, 1976). Some relation with nitrogen metabolism is also to be expected and there have been repeated indications of a connection between glutamate dehydrogenase, particularly the NADP-linked enzyme, and the urea cycle (Stewart & Moore, 1974; Al-Gharawi & Moore, 1977).…”

“…The NAD-and NADP-linked glutamate dehydrogenases' were assayed using the methods of Al-Gharawi & , and malate dehydrogenase was assayed using the method described by Moore & Ewaze (1976). Other enzyme assays were derived from those described in the literature by determination of optimal pH and substrate concentration.…”

“…Most of the work with sporophores used cultures grown on sterilized horse dung (Moore & Ewaze, 1976), but to facilitate comparative analysis of sporophores and their parent mycelia some cultures were grown in unstirred liquid maltose-CM medium (Stewart & Moore, 1974). Where reference is made to different stages in sporophore development, the stages were recognized using the criteria detailed by Stewart & Moore (1974).…”