Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.10.1 (ERK)
 95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Oxidation of DL-2-hydroxy 4-methylthiobutanoic acid (DL-HMB), DL-methionine (DL-MET) and L-methionine (L-MET) in chicken tissue homogenates was compared using 1-14C-labelled tracers. The pattern of oxidation of the substrates was similar at both low (0.7 mM) and high (20 mM) concentrations. The rate of conversion to 2-keto 4-methylthiobutanoic acid (KMB) was highest for DL-MET and lowest for L-MET in kidney, liver and intestinal mucosa. In breast muscle, rates for DL-MET and L-MET were similar at 0.7 mM, but DL-HMB showed the highest rate at 20 mM. Kidney contained the highest specific activity for oxidation of all three substrates. Raising the pH of liver and kidney homogenates from 7.5 to 8.6 increased the oxidation of DL-MET, exclusively. Experiments with inhibitors of D-2-hydroxy acid dehydrogenase (EC 1.1.99.6) and L-2-hydroxy acid oxidase (EC 1.1.3.15) suggested that D- and L-HMB were stereospecifically oxidized by the enzymes. KMB stimulated L-MET oxidation in kidney yet inhibited L-MET oxidation in liver homogenates. The effect of KMB on DL-MET and DL-HMB oxidation also varied between tissues. Amino-oxyacetate inhibited L-MET oxidation completely and DL-MET and DL-HMB oxidation almost completely in both kidney and liver. L-Cycloserine was less potent than amino-oxyacetate and decreased L-MET oxidation more in kidney than in liver. It can be calculated from the results that, at low substrate concentrations, the liver contributes principally to the whole body oxidation of both DL-HMB and DL-MET. At high (greater than physiological) concentrations, DL-HMB would be oxidized principally in skeletal muscle. At all concentrations, L-MET would be converted to KMB mainly in the muscle.
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PMID:Oxidation of methionine and 2-hydroxy 4-methylthiobutanoic acid stereoisomers in chicken tissues. 278 90

Previous evidence shows that the extensive catabolism of dietary essential amino acids (AA) by the intestine results in decreased availability of these AA for protein synthesis in extraintestinal tissues. This raises the possibility that extraintestinal availability of AA may be improved by supplying the animal with an AA source more of which can bypass the intestine. To test this hypothesis, six barrows (35-day-old, 8.6 +/- 1.4 kg), implanted with arterial, portal, and mesenteric catheters, were fed a DL-methionine (DL-MET) or DL-2-hydroxy-4-methylthiobutyrate (DL-HMTB) diet once hourly and infused intramesenterically with 1% p-amino hippurate. Although the directly available L-MET in DL-MET diet was about 1.2-fold that in DL-HMTB diet, the net portal appearance of L-MET was not different between the two diets. Compared with the low mRNA abundance and low activity of D-2-hydroxy acid dehydrogenase (D-HADH) and l-2-hydroxy acid oxidase (L-HAOX) in the intestine, the high mRNA abundance and high activity of D-AA oxidase (D-AAOX) indicated that the intestine had a relatively higher capacity of D-MET utilization than of dl-HMTB utilization to L-MET synthesis and its subsequent metabolism. However, in contrast to the much lower D-AAOX activity (nmol/g tissue) in the stomach than in the liver and kidney, both d-HADH and L-HAOX activity in the stomach was comparable with those in the liver and/or kidney, indicating the substantial capacity of the stomach to convert DL-HMTB to L-MET. Collectively, the difference in distribution of activity and mRNA abundance of D-AAOX, D-HADH, and L-HAOX in the piglets may offer a biological basis for the similar portal appearance of L-MET between DL-MET and DL-HMTB diets, and thus may provide new important insights into nutritional efficiency of different L-MET sources.
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PMID:Methionine metabolism in piglets Fed DL-methionine or its hydroxy analogue was affected by distribution of enzymes oxidizing these sources to keto-methionine. 2007 66