Gluconeogenic enzyme

There are data from animal studies in mice, rats, and pigs that indicate that both carbohydrate metabolism and lipid metabolism may be affected by exposure to heptachlor or heptachlor epoxide (Enan et al. 1982 Halacka et al. 1974 Kacew and Singhal 1973 Pelikan 1971). Alterations in gluconeogenic enzymes and an increase in cellular steatosis in the liver have been reported. Granulomas and fibrotic liver have also been observed. In addition, hepatocellular carcinoma was identified as causally related to heptachlor in the diet in a mouse study conducted by the National Cancer Institute (NCI 1977). The existing evidence suggests that heptachlor and heptachlor epoxide are hepatic toxicants. 

Figure 6.25 The intracellular location of the gluconeogenic enzymes. The gluconeogenic enzymes are located in the cytosol, except for pyruvate carboxylase which is always present within the mitochondria phosphoenolpyruvate carboxykinase is cytoplasmic in some species including humans. Consequently phosphoenolpyruvate must be transported across the inner mitochondrial enzyme by a transporter molecule in order for gluconeogenesis to take place.

There are only five key biochemical factors that provide for the regnlation (i) snbstrate cycles (ii) regulation of phosphofrncto-2-kinase (PFK-2) (iii) phosphorylation/ dephosphorylation interconversion cycles (i.e. reversible phosphorylation) (iv) gene expression of gluconeogenic enzymes (v) concentrations of precnrsors in the blood. 

Cycles arise becanse both the glycolytic and gluconeogenic enzymes are simnltaneously active. Consequently, an increase in gluconeogenic flux can be achieved either by a decrease in the activity of the glycolytic enzyme(s) and/or an increase in the activity of the gluconeogenic enzyme(s). 

Cortisol regulates gluconeogenesis by activation of genes which express some gluconeogenic enzymes so that the concentration of these enzymes is increased. 

The specific gluconeogenic enzymes in the liver of the foetus develop late in pregnancy, so that premature babies can develop hypoglycaemia soon after birth and provision of glucose is essential for their survival. 

Three irreversible steps in the glycolytic pathway are bypassed by reactions catalyzed by gluconeogenic enzymes (1) conversion of... 

TCDD, but pyruvate kinase, a glycolytic enzyme, was not affected (Weber et al. 1991a). It was also shown that changes in gluconeogenic enzyme activities preceded hormonal changes (insulin,... 

Gupta, D., Raju, J. and Baquer, N.Z. (1999) Modulation of some gluconeogenic enzyme activities in diabetic rat liver and kidney effect of anti-diabetic compounds. Indian journal of Experimental Biology 37(2), 196-199. 

Nishimura, M., and Beevers, H. 1979. Subcelluiar distribution of gluconeogenic enzymes in germinating castor bean endosperm. Plant Physiol 64,31-37. 

Dohm, G. L., Kasporek, C, J, and Barakat, H. A. (1985), Time course of changes in gluconeogenic enzyme activities during exercise and recovery. Airi. /. Piiysiai 249, E6-E11,... 

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