Glutamic-Aspartic Transaminase. XI. Reactivity toward Thiosemicarbazide<sup>*</sup>

Jenkins, W. Terry; D'Ari, Linda

doi:10.1021/bi00873a018

Cited by 33 publications

(23 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The maleate can bind noncovalently to the PLP form of AspAT, which increases the pK a of the internal aldimine between N⑀ of Lys-258 and C4Ј of PLP (34,35), whereas 2MeAsp binds to the PLP form of AspAT and forms an external aldimine complex. The K d values of these inhibitors were obtained by fitting the absorbance changes at 430 nm (36) to theoretical curves.…”

Section: Methodsmentioning

confidence: 99%

The Novel Substrate Recognition Mechanism Utilized by Aspartate Aminotransferase of the Extreme Thermophile Thermus thermophilus HB8

Nobe

Kawaguchi

Ura

et al. 1998

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

Section: Methodsmentioning

confidence: 99%

The Novel Substrate Recognition Mechanism Utilized by Aspartate Aminotransferase of the Extreme Thermophile Thermus thermophilus HB8

Nobe

Kawaguchi

Ura

et al. 1998

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…coli strains its formation was found to be induced by limiting amounts of orthophosphate in the medium [3,4]. It has been purified [5-71 and its specificity and kinetics studied in great detail [8,9]. The active E. coli enzyme is built of two protein monomers and Zn" is needed to obtain the dimer which exhibits alkaline phosphatase activity [lo-181.…”

mentioning

confidence: 99%

Some Properties of Alkaline Phosphatase of Pseudomonas fluorescens

Friedberg

Avigad

1967

European Journal of Biochemistry

View full text Add to dashboard Cite

The formation of alkaline phosphatase in a strain of Pseudomonas fluorescens was found to be induced by limiting quantities of orthophosphate in the extracellular medium. The substrate specificity of this enzyme seemed to be similar to that of Escherichia coli. On the other hand, it had some properties different from those of the E. coli enzyme. The Pseudomonas enzyme was several hundred fold more sensitive to inhibition by EDTA, but was not inhibited by cyanide and by various mercaptans. The apparent Km for p‐nitrophenylphosphate was 2.0x10−4 M and Ki for orthophosphate as a competitive inhibitor was 3.7 × 10−5 at pH 8.6.

show abstract

“…2). Addition of the substrates decreases the rate of exchange such that between 1 and 6 hr only seven peptide hydrogens exchange instead of the 17 in the free pyridoxal form, 10 hydrogens being retarded by the conversion. Thus, the number of hydrogens affected in their exchange rate by the formation of the covalent intermediates is equal to the difference of 16 hydrogens manifest at the time of intraexchange conversion plus the 10 hydrogens shown to be retarded by the conversion, i.e., to about 26 hydrogens or 6% of the total 411 peptide hydrogens per subunit.…”

Section: Resultsmentioning

confidence: 99%

“…It was decreased to 45% of this value when D20 was substituted for water in the assay. The pyridoxamine form of the enzyme was prepared from the pyridoxal form by addition of 4 mM cysteine sulfinate (10) and subsequent gel filtration.…”

mentioning

confidence: 99%

Syncatalytic conformational changes in aspartate aminotransferase determined by hydrogen-deuterium exchange.

Kägi¹,

Christen²

1978

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Catalysis-linked conformational transitions of aspartate aminotransferase (cytosolic isoenzyme from pig heart; L-aspartate:2-oxoglutarate aminotransferase, EC 2.6.1.1) have been probed by infrared spectrophotometric measurement of hydrogen-deuterium exchange. In the unliganded pyridoxal form of the enzyme at pH 6.0 and 200, 43% of the total 411 peptide hydrogens per subunit exchange within the first 10 min. An additional 9% exchange slowly in the following time period to 360 min. A quite similar exchange curve is obtained with the pyridoxamine form of the enzyme, indicating close correspondence in conformation of both unliganded forms of the enzyme. Formation of a nonproductive adsorption complex of the pyridoxal enzyme with 2-oxoglutarate or of the pyridoxamine enzyme with glutamate alters the exchange characteristics only slightly. In contrast, the formation of an equilibrium mixture of the covalent transamination intermediates, which occurs in the simultaneous presence of the amino acid and the keto acid substrate, results in a marked retardation of hydrogen exchange, reflecting a substantial tightening of the structure of the enzyme. The exchange reactions of at least 26 peptide hydrogens per subunit (6% of the total) are retarded by a factor of 6 on the average. The occurrence of such syncatalytic conformational changes reflects energetic coupling of the covalency changes at the active site with conformational changes of the macromolecular protein matrix that may contribute to optimizing the free energy profile of enzymic transamination.Conformational changes of enzymes concomitant to the binding of substrate or other specific ligands are amply documented by experiment. The changes are established as the basis for mechanisms of regulation and are also thought to contribute to both the specificity and efficiency of enzymic catalysis (1, 2). The occurrence of conformational adaptations of enzymes during the subsequent phase of catalysis, i.e., during the covalency changes, has been postulated on the basis of thermodynamic arguments (3,4). Syncatalytic adjustment of the conformation of an enzyme might optimize the free energy profile of the bond rearrangement steps. However, experimental evidence for such transient changes in conformation is scarce; their detection might be possible only under especially favorable circumstances.In aspartate aminotransferase (L-aspartate:2-oxoglutarate aminotransferase, EC 2.6.1.1) the occurrence of syncatalytic conformational changes has been indicated by differential chemical modifications. Both in the mitochondrial isoenzyme from chicken and pig (5) and in the cytosolic isoenzyme from pig (6), the reactivity of a nonessential cysteinyl residue toward sulfhydryl reagents is enhanced by one or two orders of magnitude, respectively, when the enzyme undergoes the bond rearrangement steps of transamination. In the present study, the conformational behavior of aspartate aminotransferaseThe costs of publication of this article were defrayed in part by the payment of page ch...

show abstract

Glutamic-Aspartic Transaminase. XI. Reactivity toward Thiosemicarbazide^*

Cited by 33 publications

References 12 publications

The Novel Substrate Recognition Mechanism Utilized by Aspartate Aminotransferase of the Extreme Thermophile Thermus thermophilus HB8

The Novel Substrate Recognition Mechanism Utilized by Aspartate Aminotransferase of the Extreme Thermophile Thermus thermophilus HB8

Some Properties of Alkaline Phosphatase of Pseudomonas fluorescens

Syncatalytic conformational changes in aspartate aminotransferase determined by hydrogen-deuterium exchange.

Contact Info

Product

Resources

About

Glutamic-Aspartic Transaminase. XI. Reactivity toward Thiosemicarbazide*

Cited by 33 publications

References 12 publications

The Novel Substrate Recognition Mechanism Utilized by Aspartate Aminotransferase of the Extreme Thermophile Thermus thermophilus HB8

The Novel Substrate Recognition Mechanism Utilized by Aspartate Aminotransferase of the Extreme Thermophile Thermus thermophilus HB8

Some Properties of Alkaline Phosphatase of Pseudomonas fluorescens

Syncatalytic conformational changes in aspartate aminotransferase determined by hydrogen-deuterium exchange.

Contact Info

Product

Resources

About

Glutamic-Aspartic Transaminase. XI. Reactivity toward Thiosemicarbazide^*