Glucose-1-phosphate enzymes affecting

Insulin a polypeptide hormone, M, 5,780 (bovine), synthesized in, and secreted by, the B cells of the islets of Langerhans. The first protein primary sequence ever to be elucidated was that of I. (Fig.l) [F. Sanger etal. Biochem. J. 59 (1955) 509-518], I. is the only hormone that decreases the blood glucose concentration. It affects the entire intermediary metabolism, especially of the liver, adipose tissue and muscle. I. increases the permeability of cells to monosaccharides, amino aci and fatty acids, and it accelerates glycolysis, the pentose phosphate cycle, and, in the liver, glycogen synthesis. It promotes the biosynthesis of fatty adds and proteins. These indirect effects on various enzymes and metabolic processes are listed in the tables. 

PG activity was assayed from cells grown in a medium containing 1% glucose in one-litre self-induced anaerobic fermentation for 5 days by increase of reducing sugars. Enzyme activity increased from pH 3.0 to pH 5.0 (citrate buffer) and decreased drastically above 5.0 (phosphate buffer), but activity was not affected differentially by the two buffers used (data not shown). PG activity increased almost linearly from 20°C to 40°C but above this optimum, activity was lost rapidly and the enzyme was completely inactivated at 60°C and 70°C after 10 and 6 min, respectively (data not shown). No PL, PGL or PME were detected. 

We have seen how [S] affects the rate of a simple enzymatic reaction (S—>P) with only one substrate molecule. In most enzymatic reactions, however, two (and sometimes more) different substrate molecules bind to the enzyme and participate in the reaction. For example, in the reaction catalyzed by hexokinase, ATP and glucose are the substrate molecules, and ADP and glucose 6-phosphate are the products ... 

Chemical analysis shows that whether we start with, say, 20mMglucose 1-phosphate (but no glucose 6-phosphate) or with 20 imt glucose 6-phosphate (but no glucose 1-phosphate), the final equilibrium mixture at 25 °C and pH 7.0 will be the same 1 imt glucose 1-phosphate and 19 mMglucose 6-phosphate. (Rememberthat enzymes do not affect the point of equilibrium of a reaction they merely hasten its attainment.) From these data we can calculate the equilibrium constant ... 

The following classes of phosphorus-containing compounds were not affected by large amounts of the enzyme with Mg2+, Mn2+, Zn2+, or Co2+ at either pH 9.1 or 7.5 (1) ribo- or deoxyribonucleoside mono-, di-, or triphosphates (2) ribo- or deoxyribopolynucleotides (3) nucleotide coenzymes (e.g., DPN+, UDP-glucose) (4) phosphomonoesters (e.g., glucose-6-P, p-nitrophenyl phosphate) (5) cyclic tri- or tetrametaphos-phates (6) phosphorofluoridates (inorganic phosphorofluoridate, adenosine 5 -phosphorofloridate) and (7) phosphonates (e.g., methylene-bis-phosphonate) (12, 57). 

It is becoming increasingly evident that a number of adverse reactions to drugs are due to genetically transmitted inborn enzyme abnormalities or deficiencies. The best known example of this category is the hereditary relative deficiency of the enzyme glucose-6-phosphate-dehydrogenase (G-6-PD), which occurs in 5% to 10% of Mediterranean littoral races, blacks, Pakistanis, and Sephardic Jews. This condition renders affected individuals susceptible to acute hemolytic ane-... 

Stevens and Stevens (1979) measured the hydration dependence of glucose-6-phosphate dehydrogenase, hexokinase, fumarate hydratase (fumarase), and glucose-6-phosphate isomerase (phosphoglucose isom-erase) over the range 0.1-0.6 h. Serum albumin was used as a carrier protein to buffer the water content. The hydration isotherms of the enzymes and the serum albumin were assumed to be similar. For the first three enzymes activity was detected (0.05% of full solution activity) near 0.2 h. Activity was measurable for the isomerase at 0.15 h. In all cases, even at 0.3 h, the activity in the powder was less than 5% of the solution rate. Diffusion of substrates in the powder may be rate limiting. The amount of albumin in the powder affected the rate. 

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