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)

A previously found proteinase possibly involved in the modification of hexokinase to eliminate the mitochondria-binding ability without appreciable change in the catalytic activity (called hexokinase-processing enzyme hereafter), was purified by sequential chromatographies from rat liver and its properties were examined. The hexokinase-processing enzyme had carbohydrate moieties as evidenced by adsorption on immobilized concanavalin A, and had a molecular weight of about 23,000 as estimated by SDS-PAGE and gel filtration chromatography. Benzyloxycarbonyl-phenylalanyl-L-arginine-4-methylcoumaryl-7-amide (Z-Phe-Arg-MCA)-hydrolyzing activity was co-purified with this processing activity throughout the purification, while the hydrolyzing activity for benzyloxycarbonyl-L-arginyl-L-arginine-4-methylcoumaryl-7-amide (Z-Arg-Arg-MCA) was not. The processing activity, as well as Z-Phe-Arg-MCA hydrolyzing activity, was highly sensitive to cysteine proteinase inhibition, for example, by leupeptin and N-[N-3-(trans-carboxirane-2-carbonyl)-L-leucyl]agmatine (E-64). Furthermore, the enzyme preparation reacted with an antibody against cathepsin L purified from rat kidney. These results indicated that cathepsin L may be involved in the above-mentioned processing of hexokinase.
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PMID:Possible involvement of cathepsin L in processing of rat liver hexokinase to eliminate mitochondria-binding ability. 142 31

Changes in amount and activity of enzyme protein are critical factors in regulating intracellular metabolisms. However, since the metabolisms are proceeding in environment with complex architecture consisted of various membranes, spatial factors should be taken into consideration for the regulation. In this review, involvement of interaction between cytosolic and membrane proteins in metabolic regulation are discussed. It had been reported that hexokinase activity was found in mitochondrial fraction in spite of almost exclusive distribution of other glycolytic enzymes to soluble fraction, the tendency being marked in the brain and many types of tumor cells whereas mitochondrial hexokinase activity was quite low in the liver. Interested in such enzyme and tissue specificities, we investigated the significance and mechanism of the unique intracellular distribution of hexokinase. We found that mitochondria-bound hexokinase was more active than the cytosolic type in producing glucose 6-phosphate (G6P), probably due to the advantage in utilizing ATP produced in mitochondria. In addition, we also found that the binding stabilized hexokinase against G6P inhibition. As to the binding, it was reported that G6P released hexokinase from mitochondria while Mg2+ promoted the binding. In this respect, we found that polyamines promoted the binding at much lower concentration than that of Mg2+, and mitochondria-bound form had small hydrophobic domain at terminal region for the binding to porin on the outer membrane. Then, we found a protease which specifically cleaved the domain with little effect on catalytic activity and molecular size of the bindable form. Such a modifying protease was purified and identified as lysosomal cathepsin L. The protease activity was high in the liver and low in the brain, suggesting that the difference in the activity was responsible for the afore-mentioned tissue specificity. On the other hand, we examined regulatory mechanism for active oxygen production in neutrophils, since the production of superoxide anion (O2-) by NADPH oxidase was very low at the resting state while markedly increased on phagocytosis and chemical stimulation. Since the stimulants for the activation were so various in chemical nature, we postulated mechanism to converge the stimulation to the activation. Incidentally, we found increase in phosphorylation of 46-47 K protein, irrespective of the type of stimulation. Use of inhibitors and examination on the phosphorylation condition indicated protein kinase C (PKC) as the phosphorylating enzyme. In addition, we observed the 46-47 K protein existed in cytosol at resting state, while it was translocated to cell membranes in concurrence with the phosphorylation. Similar findings were obtained in many laboratories and those proteins were named cytosolic activating factors (and then p47-phox, etc.). These proteins associate with membrane proteins to constitutes the active from of NADPH oxidase. Next, we examined mechanism to shut off the O2- production, and found that the inactivation through disassembly of the constituents was attained by dephosphorylation of phosphorylated p47-phox by cytosolic protein phosphatase. Then we have also found that protein kinases other than PKC were involved in regulation of NADPH oxidase activity. Though phosphorylation of p47-phox etc. is deeply involved in the activation of NADPH oxidase, membrane perturbation, so-called priming, is required for the activation. We also reported some possible indications for the priming, and possible involvement of cytoskeletons in O2- production. Apart from protein phosphorylation, it has been reported that amphiphilic acidic compounds are potent activator for NADPH oxidase. We also have examined their effects to find that these compounds also caused the assembly of the NADPH oxidase constituents. Reversely, amphiphilic basic compounds suppressed suggesting significance of introduction of negative charge in NADPH oxidase activat
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PMID:[Cooperation of membrane proteins and cytosolic proteins in metabolic regulation--involvement of binding of hexokinase to mitochondria in regulation of glucose metabolism and association and complex formation between membrane proteins and cytosolic proteins in regulation of active oxygen production]. 992 8

Depletion of mitochondrial DNA (mtDNA) or treatment with mitochondrial poison CCCP initiates mitochondrial stress signaling, which operates through altered Ca2+ homeostasis. In C2C12 rhabdomyoblasts and A549 human lung carcinoma cells mitochondrial stress signaling activates calcineurin and a number of Ca2+ responsive factors including ATF, NFAT, CEBP/delta and CREB. Additionally, PKC and MAP kinase are also activated. A number of nuclear gene targets including those involved in Ca2+ storage/release (RyR1, calreticulin, calsequestrin), glucose metabolism (hexokinase, pyruvate kinase, Glut4), oncogenesis (TGFbeta1, cathepsin L, IGFR1, melanoma antigen) and apoptosis (Bcl-2, Bid, Bad, p53) are upregulated. Mitochondrial stress in both C2C12 myoblasts and A549 cells induced morphological changes and invasive phenotypes. These cells also showed markedly increased resistance to etoposide-induced apoptosis that is a hallmark of highly invasive tumors. Our results describe a new mechanism of altered nuclear gene expression and phenotypic changes triggered by mitochondrial dysfunction and mtDNA damage.
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PMID:Mitochondria-to-nucleus stress signaling in mammalian cells: nature of nuclear gene targets, transcription regulation, and induced resistance to apoptosis. 1597 49