Metabolism of ethylmalic acids by Pseudomonas aeruginosa

Rabin, Robert; Саламон, Іван; Bleiweis, Arnold S.; Carlin, J.; Ajl, Samuel J.

doi:10.1021/bi00841a048

Cited by 36 publications

(21 citation statements)

References 43 publications

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“…An exception is the paper of Rabin et al (1968) that reports on the conversion of 2-oxovalerate, 4-methyl-2-oxovalerate, and 2-oxohexanoate by an IPMS activity from Pseudomonas aeruginosa at yields comparable to those reported here. Our results indicate that the IPMSs from Arabidopsis and E. coli can use 2-oxo acids ranging in length from glyoxylate to 2-oxohexanoate.…”

Section: Ipmss Produce Other Products In Vitro and In Vivocontrasting

confidence: 48%

“…For example, the reported reaction rates for 2-oxobutyrate are usually higher than those found for the true substrate 2-oxoisovalerate, despite the higher K m for 2-oxobutyrate (Webster and Gross, 1965;Strassman and Ceci, 1967;Rabin et al, 1968;Gross, 1970;Kohlhaw and Leary, 1970;Ulm et al, 1972;Wiegel and Schlegel, 1977;Wiegel, 1981;Kohlhaw, 1988). This is also true for the Arabidopsis enzymes.…”

Section: Ipmss Produce Other Products In Vitro and In Vivomentioning

confidence: 99%

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Two Arabidopsis Genes (IPMS1 and IPMS2) Encode Isopropylmalate Synthase, the Branchpoint Step in the Biosynthesis of Leucine

et al. 2006

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Heterologous expression of the Arabidopsis (Arabidopsis thaliana) IPMS1 (At1g18500) and IPMS2 (At1g74040) cDNAs in Escherichia coli yields isopropylmalate synthases (IPMSs; EC 2.3.3.13). These enzymes catalyze the first dedicated step in leucine (Leu) biosynthesis, an aldol-type condensation of acetyl-coenzyme A (CoA) and 2-oxoisovalerate yielding isopropylmalate. Most biochemical properties of IPMS1 and IPMS2 are similar: broad pH optimum around pH 8.5, Mg 21 as cofactor, feedback inhibition by Leu, K m for 2-oxoisovalerate of approximately 300 mM, and a V max of approximately 2 3 10 3 mmol min 21 g 21 . However, IPMS1 and IPMS2 differ in their K m for acetyl-CoA (45 mM and 16 mM, respectively) and apparent quaternary structure (dimer and tetramer, respectively). A knockout insertion mutant for IPMS1 showed an increase in valine content but no changes in Leu content; two insertion mutants for IPMS2 did not show any changes in soluble amino acid content. Apparently, in planta each gene can adequately compensate for the absence of the other, consistent with available microarray and reverse transcription-polymerase chain reaction data that show that both genes are expressed in all organs at all developmental stages. Both encoded proteins accept 2-oxo acid substrates in vitro ranging in length from glyoxylate to 2-oxohexanoate, and catalyze at a low rate the condensation of acetyl-CoA and 4-methylthio-2-oxobutyrate, i.e. a reaction involved in glucosinolate chain elongation normally catalyzed by methylthioalkylmalate synthases. The evolutionary relationship between IPMS and methylthioalkylmalate synthase enzymes is discussed in view of their amino acid sequence identity (60%) and overlap in substrate specificity.

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Section: Ipmss Produce Other Products In Vitro and In Vivocontrasting

confidence: 48%

Section: Ipmss Produce Other Products In Vitro and In Vivomentioning

confidence: 99%

Two Arabidopsis Genes (IPMS1 and IPMS2) Encode Isopropylmalate Synthase, the Branchpoint Step in the Biosynthesis of Leucine

et al. 2006

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“…lb. In fact, some of the leucine enzymes in other organisms carry out these analogous reactions in vitro (17,20,24,(27)(28)(29)34) and in some (9,11,20,(27)(28)(29).…”

Section: Discussionmentioning

confidence: 99%

Amino Acid Biosynthesis in the Spirochete Leptospira : Evidence for a Novel Pathway of Isoleucine Biosynthesis

1974

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Radioactive carbon dioxide was incubated with growing cells of Leptospira interrogans serotypes semaranga and tarassovi , and the specific activities and distribution of the label within the cellular amino acids were determined. The origins of the carbon skeletons of all the acid-stable amino acids except isoleucine were found to be consistent with known biosynthetic pathways for these amino acids. Experiments using radioactive carbon dioxide and other tracers indicated that most of the isoleucine was synthesized by a pathway not involving threonine. The origin of the carbon skeleton of isoleucine consisted of two residues of pyruvate (carbons 2 and 3) and acetate of acetyl-coenzyme A by this pathway. Isotope competition studies indicated that the pathway was regulated by isoleucine. The results are discussed in relation to two proposed pathways of isoleucine biosynthesis involving citramalate as an intermediate.

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“…The mechanism requires an active-site general base to accept a proton from the 3-hydroxyl concomitant with transfer of a hydride from C 3 of 6PG to C 4 of the nicotinamide ring of NADP. The resulting 3-keto intermediate is decarboxylated to give the enol of ribulose 5-phosphate followed by tautomerization of the enol to the keto product with the assist of a second enzyme residue acting as a general acid.The reaction catalyzed by 6PDGH is similar in nature to those catalyzed by isocitrate dehydrogenase (7, 8), malic enzyme (9, 10), tartrate dehydrogenase (11), and isopropylmalate dehydrogenase (12,13) in that all yield a ketone, CO 2 , and NAD(P)H as products. However, unlike other enzymes in the class, 6PDGH does not require a divalent metal ion † This work was supported by…”

mentioning

confidence: 89%

“…The reaction catalyzed by 6PDGH is similar in nature to those catalyzed by isocitrate dehydrogenase (7, 8), malic enzyme (9, 10), tartrate dehydrogenase (11), and isopropylmalate dehydrogenase (12,13) in that all yield a ketone, CO 2 , and NAD(P)H as products. However, unlike other enzymes in the class, 6PDGH does not require a divalent metal ion † This work was supported by…”

mentioning

confidence: 89%

Oxidative Decarboxylation of 6-Phosphogluconate by 6-Phosphogluconate Dehydrogenase Proceeds by a Stepwise Mechanism with NADP and APADP as Oxidants

et al. 1998

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Primary kinetic deuterium, 13C, and multiple deuterium/13C-isotope effects on V/K6PG have been measured for the Candida utilis (cu) and sheep liver (sl) 6-phosphogluconate dehydrogenases (6PGDH). With NADP as the dinucleotide substrate, the following values of D(V/K6PG), 13(V/K6PG)H, and 13(V/K6PG)D were measured at pH 8 for cu6PGDH (sl6PGDH): 1.57 +/- 0.08 (1.87 +/- 0.10), 1.0209 +/- 0.0005 (1.0059 +/- 0.000 10), 1.0158 +/- 0.0001 (1.0036 +/- 0.0008). With APADP as the dinucleotide substrate, values for the above isotope effects at pH 8 are as follows: 2.98 +/- 0.08 (2.47 +/- 0.06), 1. 0106 +/- 0.0002 (1.0086 +/- 0.000 09), and 0.9934 +/- 0.0003 (0.9950 +/- 0.0003). Results indicate the oxidative decarboxylation of 6PG to the 1,2-enediol of ribulose 5-phosphate proceeds via a stepwise mechanism with hydride transfer preceding decarboxylation in all cases. The inverse 13C-isotope effect observed with APADP and 6PG-3d may reflect a preequlibrium isotope effect on the binding of 6PG preceding hydride transfer. Deuterium-isotope effects on V, V/KNADP, and V/K6PG are identical at all pHs and for both enzymes. The primary deuterium-isotope effect on V/K6PG for both enzymes is constant at pH values below the pK in the pH profile for V/K6PG, and decreases as the pH increases. Data suggest the development of rate limitation by a step or steps other than the hydride-transfer step as the pH is increased.

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Metabolism of ethylmalic acids by Pseudomonas aeruginosa

Cited by 36 publications

References 43 publications

Two Arabidopsis Genes (IPMS1 and IPMS2) Encode Isopropylmalate Synthase, the Branchpoint Step in the Biosynthesis of Leucine

Two Arabidopsis Genes (IPMS1 and IPMS2) Encode Isopropylmalate Synthase, the Branchpoint Step in the Biosynthesis of Leucine

Amino Acid Biosynthesis in the Spirochete Leptospira : Evidence for a Novel Pathway of Isoleucine Biosynthesis

Oxidative Decarboxylation of 6-Phosphogluconate by 6-Phosphogluconate Dehydrogenase Proceeds by a Stepwise Mechanism with NADP and APADP as Oxidants

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