[120] α-Ketoglutaric dehydrogenase system and phosphorylating enzyme from heart muscle

Kaufman, Seymour

doi:10.1016/0076-6879(55)01125-7

Cited by 51 publications

(22 citation statements)

References 11 publications

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“…It is, therefore, of concern that our studies report increasing activity of a-KADH during develop ment, whereas the studies of others on a-ketoglutarate dehydrogenase, also in rat liver, reported almost constant activity during a similar time period (8). It should be noted that this reported activity was extremely low and that the spectrophotometric assay based on N A D reduction is inappropriate for the assay of this enzyme in crude preparations (10,20); in these studies (8) it was found that the a-KADH activities were unexpectedly low (about 0.3 nmol/min/mg mitochondrial protein). The presence of compounds that caused reoxidation of N A D H in crude preparations results in artificially low values (10,20).…”

Section: Discussioncontrasting

confidence: 47%

“…It should be noted that this reported activity was extremely low and that the spectrophotometric assay based on N A D reduction is inappropriate for the assay of this enzyme in crude preparations (10,20); in these studies (8) it was found that the a-KADH activities were unexpectedly low (about 0.3 nmol/min/mg mitochondrial protein). The presence of compounds that caused reoxidation of N A D H in crude preparations results in artificially low values (10,20). The method using ferricyanide as the electron acceptor (19) is applicable for crude preparations.…”

Section: Discussionmentioning

confidence: 98%

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Developmental Changes in the Enzymatic Capacity for Reduction and Oxidation of α-Ketoadipate in Rat Liver, Heart, Kidney, and Brain

1978

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Summary a-Ketoadipate, an intermediate common to lysine and tryptophan metabolism, is a substrate for both a-ketoadipate reductase (a-KAR) and a-ketoadipate dehydrogenase (a-KADH). A comparison was made of the activities of these two enzymes in liver, heart, kidney, and brain of rats during the period from 5 days before birth to 56 days after birth. In general, both enzymes increased in activity during development in all tissues tested; however, different patterns of increase were observed ( Figs. 1 and 2).The ratio of a-KADH to a-KAR (on the basis of activitylg tissue) did not change significantly in liver until day 10 and then increased 6.6-fold (from 0.08 to 0.53) in the period from day 1 0 to day 28. For other tissues the ratios increased 5.5-fold in hearts (from 0.2 to 1.1), 12-fold in kidney (from 0.2 to 2.4), and 5.3-fold in brain (from 0.3 to 1.6) during the period from day -5 to day 56.These results suggest that a-KAR has a major role in the metabolism of lysine and tryptophan during development. SpeculationIn the late fetal stage, the metabolism of a-ketoadipate depends more on reduction to a-hydroxyadipate than on oxidation to glutaryl-CoA; as development progresses there is a shift to a greater dependence on the oxidative reaction. If an analogouspattern isiresent in human development, then a-ketoadii ate metabolism in the developing individual with a-ketoadipic iciduria would remain simila; to-that of the fetal period, i n d this might explain the abnormal accumulation not only of aketoadipate but also of a-hydroxyadipate found in these individuals.The degradative route for lysine in mammals has been shown to join that of tryptophan at a-ketoadipate. a-Ketoadipate is believed then to undergo an oxidative decarboxylation to yield glutaryl-CoA and CO, (2,13,14). The enzyme catalyzing this decarboxylation is only tentatively referred to as a-ketoadipate dehydrogenase (a-KADH) because a highly purified a-ketoglutarate dehydrogenase complex has also been reported to catalyze this reaction (7,9,14). We have recently described the purification and characterization (23), as well as the subcellular localization and tissue distribution (24), of an enzyme designated a-ketoadipate reductase (a-KAR), which specifically mediates the NADH-dependent reduction of a-ketoadipate to ahydroxyadipate.Recent papers have described several human metabolic defects that involve the degradation of a-ketoadipate: a-ketoadipic aciduria (18,25,26), glutaric aciduria (5, 6, 22), and glutaric aciduria type I1 (19). An individual with a-ketoadipic aciduria, apparently resulting from a defect in the decarboxylation of aketoadipate, was reported to have increased urinary excretion not only of a-ketoadipate but also of a-hydroxyadipate (17, 25); these findings suggest the r~ssibility of an alternate route of a-ketoadipate degradation (Scrieme 1).We reported previously that a-KAR has a dominant metabolic role in tissues that have a relatively low density of mitochondria and that a-KADH has a dominant metabolic role in tissues that have ...

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Section: Discussioncontrasting

confidence: 47%

Section: Discussionmentioning

confidence: 98%

Developmental Changes in the Enzymatic Capacity for Reduction and Oxidation of α-Ketoadipate in Rat Liver, Heart, Kidney, and Brain

1978

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“…I .2). The a-ketoglutarate dehydrogenase was measured by the method of Kaufman (1955) Leach & Carr (1969). As the cell-free preparations from the two organisms showed a powerful NADH oxidase activity, those determinations which involved NADH oxidation or NAD+ reduction were performed anaerobically or in the presence of I mM-potassium cyanide; the latter completely blocked the NADH oxidase activity.…”

Section: Methodsmentioning

confidence: 99%

The Tricarboxylic Acid Cycle in Thiobacillus denitrificans and Thiobacillus-A2

Peeters

Liu

Aleem

1970

Journal of General Microbiology

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S U M M A R YThe enzymes involved in the tricarboxylic acid cycle and some other related reactions were measured quantitatively in cell-free extracts from the obligate autotroph Thiobacillus denitrijicans grown anaerobically, and in the facultative autotroph Thiobacillus-A2 grown under various conditions. The presence of an incomplete tricarboxylic acid cycle in T. denitrijicans and in Thiobacillus-A 2 (when grown autotrophically on thiosulphate) is described. The cell-free extracts from these two organisms lacked a-ketoglutarate dehydrogenase and succinyl CoA synthetase. The data from Thiobacillus-A z grown on succinate, aerobically or anaerobically, and on glutamate aerobically suggest that both the enzymes are repressed during autotrophic growth. Results are further discussed in relation to possible reasons for autotrophy.

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“…The concentration of succinohydroxamic acid was calculated by using an absorption coefficient of 61.0 mM-' (38).…”

mentioning

confidence: 99%

“…Succinyl-CoA synthetase was assayed by a published method (38) that was modified to bring the incubation conditions close to those used for the ALA synthase assay. Incubations were done in 1.5-ml microcentrifuge tubes at 37°C for 30 min in a total volume of 0.5 ml containing 800 mM NH2OH (neutralized), 100 mM Tricine (pH 7.9), 100 mM disodium succinate, 5 mM ATP, 5 mM MgCl2, 1 mM dithiothreitol, 0.4 mM CoA, and cell extract containing approximately 1 mg of protein.…”

mentioning

confidence: 99%

Cloning and sequence of the Salmonella typhimurium hemL gene and identification of the missing enzyme in hemL mutants as glutamate-1-semialdehyde aminotransferase

et al. 1990

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Salmonella typhimurium forms the heme precursor delta-aminolevulinic acid (ALA) exclusively from glutamate via the five-carbon pathway, which also occurs in plants and some bacteria including Escherichia coli, rather than by ALA synthase-catalyzed condensation of glycine and succinyl-coenzyme A, which occurs in yeasts, fungi, animal cells, and some bacteria including Bradyrhizobium japonicum and Rhodobacter capsulatus. ALA-auxotrophic hemL mutant S. typhimurium cells are deficient in glutamate-1-semialdehyde (GSA) aminotransferase, the enzyme that catalyzes the last step of ALA synthesis via the five-carbon pathway. hemL cells transformed with a plasmid containing the S. typhimurium hemL gene did not require ALA for growth and had GSA aminotransferase activity. Growth in the presence of ALA did not appreciably affect the level of extractable GSA aminotransferase activity in wild-type cells or in hemL cells transformed with the hemL plasmid. These results indicate that GSA aminotransferase activity is required for in vivo ALA biosynthesis from glutamate. In contrast, extracts of both wild-type and hemL cells had gamma,delta-dioxovalerate aminotransferase activity, which indicates that this reaction is not catalyzed by GSA aminotransferase and that the enzyme is not encoded by the hemL gene. The S. typhimurium hemL gene was sequenced and determined to contain an open reading frame of 426 codons encoding a 45.3-kDa polypeptide. The sequence of the hemL gene bears no recognizable similarity to the hemA gene of S. typhimurium or E. coli, which encodes glutamyl-tRNA reductase, or to the hemA genes of B. japonicum or R. capsulatus, which encode ALA synthase. The predicted hemL gene product does show greater than 50% identity to barley GSA aminotransferase over its entire length. Sequence similarity to other aminotransferases was also detected.

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[120] α-Ketoglutaric dehydrogenase system and phosphorylating enzyme from heart muscle

Cited by 51 publications

References 11 publications

Developmental Changes in the Enzymatic Capacity for Reduction and Oxidation of α-Ketoadipate in Rat Liver, Heart, Kidney, and Brain

Developmental Changes in the Enzymatic Capacity for Reduction and Oxidation of α-Ketoadipate in Rat Liver, Heart, Kidney, and Brain

The Tricarboxylic Acid Cycle in Thiobacillus denitrificans and Thiobacillus-A2

Cloning and sequence of the Salmonella typhimurium hemL gene and identification of the missing enzyme in hemL mutants as glutamate-1-semialdehyde aminotransferase

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