Glycolysis aerobic

The major biochemical features of neutrophils are summarized in Table 52-8. Prominent feamres are active aerobic glycolysis, active pentose phosphate pathway, moderately active oxidative phosphorylation (because mitochondria are relatively sparse), and a high content of lysosomal enzymes. Many of the enzymes listed in Table 52-4 are also of importance in the oxidative metabolism of neutrophils (see below). Table 52-9 summarizes the functions of some proteins that are relatively unique to neutrophils. 

The electron transport chain gets its substrates from the NADH and FADH2 supplied by the TCA cycle. Since the TCA cycle and electron transport are both mitochondrial, the NADH generated by the TCA cycle can feed directly into oxidative phosphorylation. NADH that is generated outside the mitochondria (for example, in aerobic glycolysis) is not transported directly into the mitochondria and oxidized—that would be too easy. 

C5a and C5a des Arg stimulate aerobic glycolysis, hexose monophosphate shunt activity, glucose uptake and the respiratory burst of human neutrophils. All of these processes are stimulated in neutrophil suspensions incubated in the absence of cytochalasin B, but the responses are considerably enhanced if this inhibitor of microtubule assembly is present. Stimulated rates of oxidative metabolism are maximal within 2 min of addition of peptides, with half-maximal responses obtained at 30-60 nM C5a and 1-3 pM C5a des Arg. 

Pyruvate kinase the last enzyme in aerobic glycolysis, it catalyzes a substrate-level phosphorylation of ADP using the high-energy substrate phosphoenolpyruvate (PEP). Pyruvate kinase is activated by fructose 1,6-bisphosphate from the PFK-1 reaction (feedforward activation). 

The total ATP from aerobic glycolysis will depend on which shuttle is used. These numbers are approximations ... 

Figure 6.3 (a) Glucose and glycogen as substrates for aerobic and anaerobic glycolysis. For aerobic glycolysis, pyruvate is converted to acetyl-CoA for anaerobic glycolysis pyruvate is converted to lactate. 

Figure 6.4 Glycolysis divided into five stages. It is not clear whether the reaction in which pyruvate is converted to acetyl-CoA, catalysed by pyruvate dehydrogenase, should be classified as a glycolytic enzyme or an enzyme of the Krebs cycle. Since the enzyme presents acetyl-CoA to the cycle, it is considered in this book as an enzyme of glycolysis (i.e. aerobic glycolysis).

A. Glycolysis shown as one of the essential pathways of energy metabolism. B. Reactions of aerobic glycolysis. C. Reactions of anaerobic glycolysis. 

Definition of aerobic and anaerobic glycoly sis Aerobic glycolysis, in which pyruvate is the end-product, occurs in cells with mitochondria and an adequate supply of oxygen. Anaerobic glycolysis, in which lactic acid is the end product, occurs in cells that lack mitochondria or in cells deprived of sufficient oxygen. 

Pellerin L. and Magistretti P J. (1994). Glutamate uptake into astrocytes stimulates aerobic glycolysis a mechanism coupling neuronal activity to glucose utilization. Proc. Natl. Acad. Sci. USA 91 10625-10629. 

Hochachka and Somero, 1977). Even glycogen and glucose are used intensively in red muscle of tuna under aerobic conditions (so-called aerobic glycolysis). In contrast, the sluggish scorpion fish and whiting can perform only relatively slow movements using the white muscle. 

Berberine inhibits oxidative decarboxylation of yeast pyruvic acid (310) the same dose has, however, no effect upon aerobic glycolysis, Warburg s respiratory enzymes, indophenol oxidase, etc. Berberine and tetrahydroberberine have an inhibitory effect on oxidation of (+ )-alanine in rat kidney homogenates (498). Berberine and palmatine show a specific inhibitory effect upon cholinesterase in rabbit spleen and on pseudocholinesterase in horse serum (499). Berberine inhibits cellular respiration in ascitic tumors and even in tissue cultures (500-502). The specific toxic effect of berberine on the respiration of cells of ascitic tumors in mice was described (310). The glycolysis was not found to be affected, but the uptake of oxygen was smaller. Fluorescence was used in order to demonstrate berberine in cellular granules. Hirsch (503) assumed that respiration is inhibited by the effect of berberine on the yellow respiratory enzymes. Since the tumorous tissue contains a smaller number of yellow respiratory enzymes than normal tissue it is more readily affected by berberine. Subcutaneous injections of berberine, palmatine, or tetrahydropalmatine significantly reduce the content of ascorbic acid in the suprarenals, which is not affected by hypophysectomy (504). 

Brain function is dependent upon ready availability of energy by aerobic metabolism. This energy is provided by aerobic glycolysis, the breakdown of glucose blood sugar to pyruvic acid with 02 as an electron acceptor. Therefore, brain cells and other nerve cells are highly susceptible to interruptions in the supply of either 02 or blood glucose. 

Glycolysis A metabolic pathway of living cells with the sequence of enzyme reactions that converts glucose into lactic acid (anaerobic glycolysis) or into pyruvate (aerobic glycolysis). 

It is accepted that the cells in tumors in vivo undergo high rates of aerobic glycolysis to produce lactate. A major substrate appears to be glutamine derived from the degradation of muscle proteins (Newsholme et al., 1985 McKeehan,... 

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