Citrate synthase, continued

Lactate dehydrogenase is closely associated with the final step in fermentative metabolism conversion of pyruvate to lactate- Citrate synthase is closely associated with oxidative metabolism, because this enzyme catalyzes the introduction of acetyl groups into the Krebs cycle. Continued operation of the Krebs cycle is dependent on the continued transfer of electrons from reduced NAD and FAD to the respiratory chain, which catalyzes the reduction of Oi to HjO. Table 4.14 lists lactate dehydrogenasc/citrate synthase activity ratios for muscles that contain a large proportion of white or red muscle fibers. The data demonstrate that the ratio is relatively high in white cell muscles but low in red cell muscles. 

How Do Enzymes Work Citrate Synthase 1045 Table 26.3 Structures of Some Common Coenzymes (continued)... 

Y-Ray crystallography can also be used to obtain dynamic information on conformational oscillations which continually perturb the native conformation. The calculated electron density of any atom in a protein crystal is a time averaged value, dependent on (a) the amount of disorder in the crystal lattice, (b) atomic vibration, and (c) rapid fluctuation between a small number of conformational substates. If the motion between these substates is large then the electron density is smeared and the polypeptide chain cannot be followed, e.g., 80 residues in the citrate (si)-synthase (E.C. 4.1.3.7) structure are like this. Refinement of high-resolution electron... 

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