Abstract
When Neurospora crassa is grown with acetate as a source of carbon and energy, the metabolic pathways differ from those occurring in hyphae grown with sucrose [1-.6]. The rates of the glycolysis and of the hexose monophosphate shunt are reduced, whereas the activities of acetyl CoA synthase, isocitrate lyase, malate synthase and phosphoenolpyruvate carboxykinase are considerably enhanced, which is essential for the utilization of acetate and gluconeogenesis. Isocitrate lyase and malate synthase are located in giyoxysomes [3], but the fulfilment of the glyoxylate cycle utilizes several enzymes of the tricarboxylic acid cycle and entails a co-operation between mitochondria and glyoxysomes. Since glyoxysomes from Neurospora do not contain citrate synthase [7], these organelles would have to import citrate or isocitrate as a substrate for isocitrate lyase. Furthermore, glyoxysomes must export succinate, and possibly malate, for further oxidation. Therefore, several mitochondrial enzymes could take on an increased significance or have an altered role when Neurospora is grown with acetate, in response to the induction of isoeitrate lyase and to the increased production of malate and succinate. It has been reported before that growth with acetate results in a 3to 5-fold increase in the activity of citrate synthase, NADP-isocitrate delaydrogenase, succinate dehydrogenase, fumarase and malate dehydrogenase [2,4-7]. There is, however, no information presently available concerning the possible changes occurring in the properties of intact mitochondria, as a response to the growth of Neurospora in a medium containing acetate. The purpose of the present work was therefore to study the oxidative and phosphorylative properties of mitochondria isolated from Neurospora grown with acetate, and to compare them with mitochondria from hyphae grown with sucrose, with particular attention given to variations occurring at different stages of growth.
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call