Kidney , enzymes function

CHRONIC HEALTH RISKS effects on central nervous system weakness fatigue depression headache possible liver damage reproductive effects peripheral neuropathy effects on blood minor effects on kidney enzyme functions increased risk of leukemia increased risk of lymphoma EPA Group C possible human carcinogen. 

Figure 6.5. Compatibility of organic osmolytes with enzyme function. (Upper panel) Pyruvate kinase of the marine crab Pachygrapsus crassipes. The effects of KC1 and NaCI and several organic solutes on the Km of phosphoenol pyruvate (PEP) (modified after Bowlus and Somero, 1979). (Middle panel) Malate dehydrogenase of the mangrove (Rhizophora mangle). Effects of NaCI and three organic osmolytes (the amino acid proline and the polyols pinitol and OMMI) on catalytic activity (modified after Sommer et al., 1990). (Bottom panel) Effects of NaCI and four osmolytes found in mammalian kidney (urea, glycine betaine, sorbitol, and inositol) on the Km of uric acid of uricase (modified after Yancey, 1992). (Figure modified after Somero and Yancey, 1997.)...

Figure 4.10 Fits to kinetic data from [135] on the operation of citrate synthase from rat kidney. Data (flux as a function of substrate concentrations) were obtained from Figures 2, 3, 4, 5, 6, 7, and 9 of [135], Initial fluxes (p.mol of COASH (or CIT) synthesized per minute per ug of enzyme) measured at the substrate concentrations indicated are plotted in A, B, C, and D. For A, B, and D, the initial product (CIT and COASH) concentrations are zero. In C, flux was measured with COASH added in various concentrations to investigate the kinetics of product inhibition. E and F show fits to kinetic data on the reverse operation of kidney enzyme, with product concentrations indicated in the figure. All data were obtained at pH = 8.1 at 28 °C. Model fits in all cases are plotted as solid lines.

The radius of Zn is 0.74 A, that of Cd is 0.95 A. Can this difference be the cause of such a dramatic reversal of biological properties The answer is that while size is not the only factor, it is very important. In the carbonic anhydrase enzyme the Zn ion is found electrostatically bonded to atoms on file protein, as shown in Figure 7.8 . It turns out that Cd binds in this same place preferentially over Zn ", thus displacing it. When Cd is present instead of Zn ", however, the reaction of CO2 with water is not facilitated. More seriously, Cd + inhibits reactions that are essential to the kidney s functioning. Moreover, cadmium is a cumulative poison, so chronic exposure to even veiy low levels over an extended time leads to poisoning. 

Acrylonitrile is beheved to behave similarly to hydrogen cyanide (enzyme inhibition of cellular metaboHsm) (150) and is befleved to be a potential carcinogen (151). It can also affect the cardiovascular system and kidney and Hver functions (150). Eurther information on the toxicology and human exposure to acrylonitrile is available (152—154) (see Acrylonitrile). 

AQP10 has only been identified in the small intestine so far and is thought to play a role in hormonal secretion. AQP11 is expressed in kidney, liver, testis and brain, but no function has been found so far. AQP12 has been identified in pancreatic acinar cells, where it is thought to facilitate the release of digestive enzymes into the pancreatic duct. 

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