Subcellular localization and properties of glyoxylate cycle enzymes in the liver of rats with alloxan diabetes.
Key enzymes of the glyoxylate cycle (isocitrate lyase and malate synthetase) were found in the liver and kidney of rats suffering from alloxan diabetes. The activities of these enzymes in the liver were 0.080 and 0.0430 U/mg protein, respectively. Isocitrate lyase activity in the kidney was 0.030 U/mg protein, and that of the malate synthetase was 0.018 U/mg protein. Peroxisomal localization of the enzymes was shown. A novel malate dehydrogenase isoform was found in a liver of rats suffering from the alloxan diabetes. The isocitrate lyase was isolated by selective (NH4)2SO4 precipitation and DEAE-Toyopearl chromatography. The resulting enzyme preparation had specific activity 6.1 U/mg protein, corresponding to 76.25-fold purification with 32.6% yield. The isocitrate lyase was found to follow the Michaelis--Menten kinetic scheme (Km for isocitrate, 0.08 mM) and to be competitively inhibited by glucose 1-phosphate (Ki = 1. 25 mM), succinate (Ki = 1.75 mM), and citrate (Ki = 1.0 mM); the pH optimum of the enzyme was 7.5 in Tris-HCl buffer.
Volvenkin
S V
SV
School of Biology and Soil Sciences, Voronezh State University, Voronezh, 394693, Russia. root@bc.vucnit.voronezh.su
Popov
V N
VN
Eprintsev
A T
AT
D000818:Animals; D001921:Brain / Q000201:enzymology; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003600:Cytosol / Q000201:enzymology; D003921:Diabetes Mellitus, Experimental / Q000201:enzymology*; D006038:Glyoxylates / Q000378:metabolism*; D007522:Isocitrate Lyase / Q000302:isolation & purification / Q000378:metabolism*; D007668:Kidney / Q000201:enzymology; D008099:Liver / Q000201:enzymology*; D008292:Malate Synthase / Q000302:isolation & purification / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000201:enzymology; D018482:Muscle, Skeletal / Q000201:enzymology; D009206:Myocardium / Q000201:enzymology; D009928:Organ Specificity; D020675:Peroxisomes / Q000201:enzymology; D051381:Rats; D013347:Subcellular Fractions / Q000201:enzymology
D006038:Glyoxylates; D008292:Malate Synthase; D007522:Isocitrate Lyase