Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P47989 (xanthine oxidase)
 8,633 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Evidence is presented that, as in cardiomyocytes, vascular endothelial cells use fatty acids, in addition to glucose, as a respiratory fuel. Attention is focused on the cardiac interstitium, lined by vascular cells and cardiomyocytes, which may be enriched with metabolic products from these cells. Also, certain proteins are present in the interstitial fluid (Qi) such as plasma proteins and fatty acid binding protein (FABP). However, the concentration of FABP is so low in Qi that albumin is more important to shuttle long chain fatty acids in the interstitial fluid between cardiomyocytes and the vascular compartment. Under hypoxic conditions (hypo)xanthine, lactate and fatty acids may be expected to accumulate in the interstitium, as well as proteins from adjacent cells, such as xanthine oxidase from endothelial cells. This enzyme, acting upon the elevated level of (hypo)xanthine, giving rise to O2-., may be involved in the damage of the ischaemic heart. The significance of the interstitium in ischaemia and in fibrosis following long standing cardiac lipidosis is briefly discussed, as well as the possible mechanisms involved in fatty acid transport in the heart.
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PMID:Substrates for energy metabolism in the heart: the role of the interstitial compartment. 366 8

Acetyl-L-carnitine (ALCAR) is intimately involved in the transport of long chain fatty acids across the inner mitochondrial membrane during oxidative phosphorylation. ALCAR also has been reported to attenuate the occurrence of parkinsonian symptoms associated with 1-methyl-1,2,3,6-tetrahydropyridine (MPTP) in vivo, and protects in vitro against the toxicity of the neurotoxic 1-methyl-4-phenylpyridinium (MPP+) metabolite of MPTP. The mechanism for these protective effects remains unclear. ALCAR may attenuate hydroxyl (HO*) free radical production in the MPTP/MPP+ neurotoxic pathway through several mechanisms. Most studies on MPTP/MPP+ toxicity and protection by ALCAR have focused on in vivo brain chemistry and in vitro neuronal culture studies. The present study investigates the attenuative effects of ALCAR on whole body oxidative stress markers in the urine of rats treated with MPTP. In a first study, ALCAR totally prevented the MPTP-induced formation of HO* measured by salicylate radical trapping. In a second study, the production of uric acid after MPTP administration-a measure of oxidative stress mediated through xanthine oxidase-was also prevented by ALCAR. Because ALCAR is unlikely to be a potent radical scavenger, these studies suggest that ALCAR protects against MPTP/MPP+-mediated oxidative stress through other mechanisms. We speculate that ALCAR may operate through interference with organic cation transporters such as OCTN2 and/or carnitine-acylcarnitine translocase (CACT), based partly on the above findings and on semi-empirical electronic similarity calculations on ALCAR, MPP+, and two other substrates for these transporters.
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PMID:Acetyl-L-carnitine prevents total body hydroxyl free radical and uric acid production induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in the rat. 1521 12

The reduction of acetaldehyde back to ethanol via NAD-linked alcohol dehydrogenase is an important mechanism for keeping acetaldehyde levels low following ethanol ingestion. However, this does not remove acetaldehyde from the body, but just delays its eventual removal. Acetaldehyde is removed from the body primarily by oxidation to acetate via a number of NAD-linked aldehyde dehydrogenase (ALDH) enzymes. There are nineteen known ALDHs in humans, but only a few of them appear to be involved in acetaldehyde oxidation. There are many analogous enzymes in other organisms. Genetic polymorphisms of several ALDHs have been identified in humans that are responsible for several hereditary defects in the metabolism of normal endogenous substrates. The best known ALDH genetic polymorphism is in ALDH2 gene, which encodes a mitochondrial enzyme primarily responsible for the oxidation of the ethanol-derived acetaldehyde. This common polymorphism is known to dominantly inhibit its enzymatic activity resulting in reduced ability to clear acetaldehyde in both homozygote and heterozygote individuals. These individuals are generally protected against alcohol abuse but are susceptible to oesophageal cancer. For those enzymes that are capable of reacting with acetaldehyde, they may do so at the expense of their normal substrates, resulting in abnormal accumulation of these substrates. Examples of this are the aldehydes of the biogenic amines, dopamine, noradrenaline, adrenaline, serotonin and long chain lipid aldehydes such as nonenal. Not all of these enzymes are capable of efficient oxidation of acetaldehyde; however, it is possible that acetaldehyde may function as an inhibitor of these enzymes as well. The aldehydes whose metabolism is interfered with may also serve as inhibitors of ALDHs as well. However, this aspect of aldehyde function has not been extensively studied. A number of other mechanisms for the removal of acetaldehyde exist. For example, reaction of acetaldehyde with protein or nucleic acids is responsible for the disappearance of a small amount of acetaldehyde, but may be responsible for some pathological effects of acetaldehyde. There are a few other enzymes such as aldehyde oxidase, xanthine oxidase, cytochrome P450 oxidase and glyceraldehyde-3-phosphate dehydrogenase that are capable of oxidizing acetaldehyde. However, these enzymes account for only a small fraction of the total activity.
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PMID:Removal of acetaldehyde from the body. 1759 Sep 85