Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.1.1 (hexokinase)
 5,274 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The rates of ATP synthesis and release by the dynein ATPase were determined in order to estimate thermodynamic parameters according to the pathway: (Formula: see text). Dynein was incubated with high concentrations of ADP and Pi to drive the net synthesis of ATP, and the rate of ATP production was monitored fluorometrically by production of NADPH through a coupled assay using hexokinase and glucose-6-phosphate dehydrogenase. The turnover number for the rate of release of ATP from 22S dynein was 0.01 s-1 per site at pH 7.0, 28 degrees C, assuming a molecular weight of 750 000 per site. The same method gave a rate of ATP synthesis by myosin subfragment 1 of 3.4 X 10(-4) s-1 at pH 7.0, 28 degrees C. The rate of ATP synthesis at the active site was estimated from the time dependence of medium phosphate-water oxygen exchange. Dynein was incubated with ADP and [18O] Pi, and the rate of loss of the labeled oxygen to water was monitored by 31P NMR. A partition coefficient of 0.31 was determined, which is equal to k-2/(k-2 + k3). Assuming k3 = 8 s-1 [Johnson, K.A. (1983) J. Biol. Chem. 258, 13825-13832], k-2 = 3.5 s-1. From the rates of ATP binding and hydrolysis measured previously (Johnson, 1983), the equilibrium constants for ATP binding and hydrolysis could be calculated: K1 = 5 X 10(7) M-1 and K2 = 14.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Rate of ATP synthesis by dynein. 293 51

Roosters homozygous for the rose comb allele (R/R) are subfertile. In previous research, these subfertile roosters were characterized by an in vitro sperm penetration assay as having limited sperm motility. The objectives in the present study were to characterize sperm motility by computer-assisted sperm motion analysis and to account for a mechanism underlying poor sperm motility. Percentages of motile sperm differed between subfertile males and fertile controls (r/r) by 29% (p < 0.001). The concentration of intracellular ATP in sperm form subfertile roosters was less than in that from fertile controls (p < 0.001). The genotypic difference is sperm motility, as measured with the sperm penetration assay, was maintained when ATP production was dependent on anaerobic glycolysis (p < 0.001). In this case, sperm were incubated with exogenous glucose and cyanide. Consequently, we could not attribute the genotypic difference in sperm mobility to mitochondrial respiration. In contrast, glucose transport, as measured by the uptake of [1,2-3H]-2-deoxy-D-glucose, was reduced in sperm from subfertile roosters (p < 0.001). Neither hexokinase nor glyceraldehyde-3-phosphate dehydrogenase activity differed between genotypes (p > 0.05). Likewise, lactate dehydrogenase activity did not differ between genotypes (p > 0.05). As evidenced by creatine kinase activity and dynein ATPase activity, neither the potential for energy transfer nor utilization within the axoneme differed between genotypes (p > 0.05). Therefore, we attribute the subfertility of roosters homozygous for the rose comb allele to decreased spermatozoal glucose transport.
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PMID:Reduced glucose transport in sperm from roosters (Gallus domesticus) with heritable subfertility. 931 82