Vitamin K-dependent carboxylase: mRNA distribution and effects of vitamin K-deficiency and warfarin treatment.

A cDNA encoding vitamin K-dependent gamma-glutamyl carboxylase was cloned from a human Hep G2 cDNA library. The RNA transcript of the enzyme was found to be widely distributed in various human and rat tissues with liver showing the highest level. The carboxylase transcription in liver was not affected in rats treated with a single dose of warfarin (10 mg/kg) when measured up to 48 hours after the dose, though, at 12 hours, carboxylase activity measured in liver microsomes was elevated 5.4 fold over controls (p < 0.001). In rats fasted for 72 hours there was no affect on transcription in the liver while hepatic carboxylase activity increased 4.1 fold (p < 0.001). These data suggest that the increase in activity of the liver carboxylase in warfarin treated or fasted rats was not regulated by transcription but more likely was due to a posttranscriptional mechanism.

[Activity of enzymes participating in xenobiotic metabolism and the condition of microsomal membranes of rat liver in vitamin K deficiency]. / Aktivnost' fermentov, uchastvuiushchikh v metabolizme ksenobiotikov, i sostoianie mikrosomal'nykh membran pecheni krys pri defitsite vitamina K.

Alimentary deficiency or vitamin K (vitamin K-poor diet) as well as the vitamin deficiency resulting from sinkumar administration are accompanied by a decreased activity of microsomal demethylases, hydroxylase, NADH- and nNADPH-reductases of dichlorophenolindophenol and neotrazolium. The activity of cytosolic enzymes (only glutathione-S-transferases, aryl- and allyl esterases) is diminished in a lesser degree. Vitamin K deficiency does not significantly interfere with the effect of the xenobiotic metabolism enzyme inducer (phenobarbital) or the cytochrome P-450 inhibitor (cobalt chloride). The changes in the enzyme activity result in a decrease of acetanilide biotransformation. A possible reason for the observed changes in the activity of microsomal enzymes is the weakening of hydrophobic and polar interactions in microsomal membranes. This hypothesis was confirmed by experiments with the use of membrane perturbants as well as by solubilization of membrane-bound enzymes.

[The effect of vitamin K deficiency in rats on various enzyme systems participating in energy metabolism]. / Vliianie nedostatochnosti vitamina K u krys na nekotorye fermentnye sistemy, uchastvuiushchie v énergoobespechenii.

In alimentary deficiency of vitamin K in rats, accompanied by an increase in the prothrombin time by 30%, activity of kidney creatine kinase and of blood serum alkaline phosphatase was unaltered, while the activity of alkaline phosphatase in small intestinal mucose was decreased by 20% and that of creatine kinase from skeletal muscles--by 10%. In vitamin K-deprived animals the rate of coupling between respiration and mitochondrial phosphorylation was decreased, which might be due to alteration in the NADH-dehydrogenase complex. Menadion reductase activity and cyanide-resistant respiration of mitochondria were unaltered in presence of menadion. Palmitic acid effectively activated of mitochondrial respiration in vitamin K-deprived animals (contrary to the control rats). This effect appears to occur as a result of structural alterations in mitochondria depending on vitamin K level in the organelles.

[The effect of vitamin K on the activity of glycolysis and pentose phosphate cycle enzymes]. / Vliianie vitamina K na aktivnost' fermentov glikoliza i pentozofosfatnogo tsikla.

Effect of naphthoquinone levels on the activity of enzymes involved in glycolysis and pentose phosphate cycles was studied in male rats. Under conditions of primary and secondary K-avitaminosis the enzymatic activity, limiting these cycles, (aldolase of fructose-1,6-diphosphate, glucose phosphate isomerase and glucose-6-phosphate dehydrogenase) was increased, while the mitochondrial glutamate dehydrogenase activity was decreased. As a result of metabolic transformations under conditions of K-avitaminosis (primary and secondary) concentration of DNA in the animal tissues was lowered.

[Tissue lipolytic activity with various vitamin K and E allowances in white rats]. / Lipoliticheskaia aktivnost' tkanei pri razlichnoi obespechennosti belykh krys vitaminami K i E.

Experiments on white male rats were performed to study the activity of tissue lipase (pH 6.8-7.2) and lipoprotein lipase (pH 8.5) in the liver, skeletal muscles and kidneys depending on the body supply with vitamins K and E. It was established that in rats with food K-avitaminosis, liver and skeletal muscle lipase and lipoprotein lipase and kidney lipoprotein lipase were activated. The analogous changes in the activity of the test enzymes were discovered in animals given antivitamins K - hydroxycoumarins (e.g. pelentan). The exception to the rule was lipase (pH 6.8-7.2) of the kidneys. E-avitaminosis was accompanied by alterations in the activity of the test enzymes in the liver, skeletal muscles and kidneys.

Vitamin K-dependent carboxylase. Solubilization and properties.

Vitamin K is required for an enzymatic carboxylation of glutamyl residues in a microsomal protein precursor of plasma prothrombin to form gamma-carboxyglutamic acid. The enzyme system (carboxylase) which catalyzes this reaction has now been solubilized by extraction of the microsomes with Triton X-100 and has been shown to fix H14CO3- as gamma-carboxyglutamic acid residues in biologically active prothrombin. Enzyme activity requires O2 and vitamin K hydroquinone or vitamin K + NADH. Unlike the microsomal-bound carboxylase, soluble carboxylase activity is independent of either ATP or Mg2+ addition and is unaffected by either the ATP analog, adenyl-5'-yl imidodiphosphate (AMP-P(NH)P, or EDTA. These observations suggest that the energy required to drive the carboxylation reaction is derived from the oxidation of the reduced form of vitamin K. Although the membrane-bound carboxylase is inhibited by Warfarin, this anticoagulant is ineffective as an inhibitor of the soluble enzyme. A second anticoagulant, 2-chloro-3-phytyl-1,4-natpthoquinone (chloro-K), differs from Warfarin in that it effectively inhibits both the membrane-bound and soluble carboxylases.

[Influence of uncoupling agents on the capacity of transamidinase in kidney and pancreas]. / Einfluss entkoppelnder Agentien auf die Transamidinase-Kapazität von Nieren und Pankreas

It was found in white rats that hyperthyreosis (0.5% thyreoidin in dry food), respectively 2,4-dinitrophenol (30 mg/kg body weight/day i. p.), deficiency of the vitamins K and E or complete fasting increase the content of creatine in muscle, plasma and urine, but reduce the concentration of creatinine. Simultaneously the elevated creatine level of blood causes a repression of transamidinase in kidneys and pancreas. The common mode of action of the mentioned agents is seen in a decoupling of the oxidative phosphorylation, and in an insufficient availability of ATP, respectively.