Some Transamination Reactions Involving Vitamin B<sub>6</sub><sup>1</sup>

Metzler, David E.; Snell, Esmond E.

doi:10.1021/ja01124a033

Cited by 254 publications

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“…The "inactive" subform (360 pg) was incubated with threo-/?-chloro-m-glutamate (25 pmoles) in 0.25 M potassium phosphate, pH 8.0, a t 27" in a final volume of 1.0 ml. After 45 minutes the formation of keto acid was measured according to the method of Metzler and Snell [17]. I n this experiment 0.02 pmole of keto acid was formed.…”

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The Reaction of β‐Chloroglutamic Acid with Glutamate‐Aspartate Transaminase

Manning

Khomutov

Fasella

1968

European Journal of Biochemistry

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Porcine glutamate-aspartate transaminase catalyzes a @-elimination reaction with both the threo-and erythro-isomers of 8-chloroglutamate ; chloride, ammonia, and a-ketoglutarate are formed in equimolar amounts. The latter product was characterized as the 2,4-dinitrophenylhydrazone and by catalytic hydrogenation of this derivative to glutamic acid.The 8-elimination reaction is catalyzed by highly purified glutamate-aspartate transaminase ; the reaction is not catalyzed by the phosphopyridoxamine form of the enzyme, the apoenzyme, or by free pyridoxal 5'-phosphate. There is no detectable transamination between B-chloroglutamate and either oxaloacetate or a-ketoglutarate. Incubation of either the holoenzyme or the apoenzyme with p-chloroglutamate does not result in any detectable loss of enzyme activity. I n the presence of N-ethylmaleimide much less a-ketoglutarate than ammonia is formed; this is consistent with the idea that a reactive carbanion intermediate reacts with N-ethylmaleimide.The novel 8-elimination reaction with glutamate-aspartate transaminase demonstrated here supports the idea that in some instances the specificity of an enzymatic reaction can be determined by the structure of the substrate.Glutamate-aspartate transaminase catalyzes the reversible transfer of an amino group fromL-aspartate to a-ketoglutarate forming oxaloacetate and L-glutamate; other amino acids can also undergo transamination with this enzyme although they are less efficient substrates than the glutamate-aspartate pair [I]. There has been considerable interest in the reaction of substrate analogues with glutamate-aspartate transaminase in an effort to elucidate some of the intermediate steps of the reaction. Thus, in a study of the reaction between the transaminase and a-methylaspartate (which lacks an a-hydrogen atom and hence cannot undergo transamination) two new absorption bands were observed, one at 430 mp and the other at 360 mp [2]. It was proposed that these are due to coenzyme-substrate aldimine derivatives analogous to those formed with the glutamateaspartate substrate pair before the loss of the a-hydrogen atom. When erythro-/3-hydroxyaspartic acid is incubated with glutamate-aspartate transaminase there is a dramatic increase in the absorption a t 490 mp; this is followed by a slow increase in the absorption a t 330 mp (attributed to the phosphopyridoxamine enzyme) and a corresponding formation Enzymes. Glutamate-aspartate transaminase, or L-aspartate: 2-oxoglutarate aminotransferase (EC 2.6.1.1) ; glutamic dehydrogenase, or L-glutamate : NAD oxidoreductase (deaminating) (EC 1.4.1.2) ; malic dehydrogenase, or L-malate: NAD oxidoreductase (EC 1.1.1.37); glutamic decarboxylase, or L-glutamate: 1-carboxy-lyse (EC 4.1.1.15).18 European J. Biochem., Vol. 5 of keto acid. However, little, if any, of the intcrmediate absorbing a t 490mp is detected when threo-@-hydroxyaspartate is the substrate. It has been suggested that the species absorbing a t 490 mp is a semiquinoid coenzyme-substrate derivative [3]. The reason for the d...

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The Reaction of β‐Chloroglutamic Acid with Glutamate‐Aspartate Transaminase

Manning

Khomutov

Fasella

1968

European Journal of Biochemistry

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“…In extending our earlier studies of non-enzymatic transamination between pyridoxal and amino acids, David Metzler showed that transamination (reaction 4) took place with most amino acids, was greatly accelerated by ions of copper, iron, or aluminum, and was fully reversible (58). With serine, a,\3-elimination (reaction 5) occurred, while, with threonine two competing reactions, 6 and 7, were observed (59).…”

Section: Pyridoxal-catalyzed Reactions Of Amino Acidsmentioning

confidence: 93%

FROM BACTERIAL NUTRITION TO ENZYME STRUCTURE: A Personal Odyssey

Snell

1993

Annu. Rev. Biochem.

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As a former editor or member of the Editorial Board of the Annual Review of Biochemistry I helped to select authors of the prefatory chapters for more than 20 years. Now I am asked to write one myself. The first such chapter appeared in 1953 with the prefatorial statement: “This is the first of a series in which it is the hope of the Editorial Committee that our elders in biochemistry will give us through chapters of a historical and philosophical character the benefit of their long years of experience in biochemistry.” With one exception, the chapters have appeared regularly ever since. Their authors comprise a group I am proud to join even while harboring some doubts about really belonging. Their autobiographical accounts have added much to our understanding of how and why they became biochemists, and how biochemistry itself developed. I shall continue in this tradition.

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“…Brgnddn et al (47) suggest that the Zn2+--OH2...OH(Ser--48)...N(His--51) system may function as a "proton charge relay" as shown in Eq. (24). This suggestion offers a plausible explanation for the afore-mentioned pHdependencies of NAD + and NADH binding to the native enzyme, as shown in Eq.…”

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Mechanisms of zinc ion catalysis in small molecules and enzymes

Dunn

Structure and Bonding

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Some Transamination Reactions Involving Vitamin B₆¹

Cited by 254 publications

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The Reaction of β‐Chloroglutamic Acid with Glutamate‐Aspartate Transaminase

The Reaction of β‐Chloroglutamic Acid with Glutamate‐Aspartate Transaminase

FROM BACTERIAL NUTRITION TO ENZYME STRUCTURE: A Personal Odyssey

Mechanisms of zinc ion catalysis in small molecules and enzymes

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Some Transamination Reactions Involving Vitamin B61

Cited by 254 publications

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The Reaction of β‐Chloroglutamic Acid with Glutamate‐Aspartate Transaminase

The Reaction of β‐Chloroglutamic Acid with Glutamate‐Aspartate Transaminase

FROM BACTERIAL NUTRITION TO ENZYME STRUCTURE: A Personal Odyssey

Mechanisms of zinc ion catalysis in small molecules and enzymes

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Some Transamination Reactions Involving Vitamin B₆¹