Stereochemistry and kinetic isotope effects in the decarboxylation of S-adenosylmethionine catalyzed by the pyruvyl enzyme, S-adenosylmethionine decarboxylase.

Allen, R R; Klinman, Judith P.

doi:10.1016/s0021-9258(19)69595-5

Cited by 21 publications

(7 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We here present with mero-DAP decarboxylase the first evidence for the enzymatic amino acid decarboxylation in an inversion mode (Scheme V). The magnitude of the optical rotation of methyl 5-phthalimido[5-2H]valerate and the Escherichia coli, a pyruvate-containing amino acid decarboxylase, operates via a retentive mode (Allen & Klinman, 1981). quantitative preservation of the deuterium labels show that the reaction is strictly stereospecific.…”

Section: Discussionmentioning

confidence: 99%

Stereochemistry of meso-.alpha.,.epsilon.-diaminopimelate decarboxylase reaction: the first evidence for pyridoxal 5'-phosphate dependent decarboxylation with inversion of configuration

Asada¹,

Tanizawa²,

Sawada³

et al. 1981

Biochemistry

View full text Add to dashboard Cite

The stereochemistry of the decarboxylation of meso-alpha,epsilon-diaminopimelate catalyzed by meso-alpha,epsilon-diaminopimelate decarboxylase (EC 4.1.1.20) of Bacillus sphaericus was determined by stereochemical analyses of [6-2H]-L-lysine produced by the reaction in D2O. The product [6-2H]-L-lysine was converted to levorotatory methyl 5-phthalimido[5-2H]valerate by the reactions not affecting the absolute configuration of the asymmetric carbon atom. By contrast, methyl 5-phthalimido[5-2H]valerate derived from [2,6-2H2]-L-lysine, which was produced from [2,6-2H2]diaminopimelate by decarboxylation in H2O, was dextrorotatory. The authentic methyl (R)-5-phthalimido[5-2H]valerate prepared from L-glutamate with glutamate decarboxylase was levorotatory. These results indicate that the meso-alpha,epsilon-diaminopimelate decarboxylase reaction proceeds in an inversion mode. The deuterium label in [6-2H]-L-lysine was fully conserved during the conversion into pelletierine through [1-2H]cadaverine by the stereospecific diamine oxidase reaction. Thus, the enzymatic decarboxylation of meso-alpha,epsilon-diaminopimelate occurs with inversion of configuration in contrast to the other amino acid decarboxylase reported so far.

show abstract

Section: Discussionmentioning

confidence: 99%

Stereochemistry of meso-.alpha.,.epsilon.-diaminopimelate decarboxylase reaction: the first evidence for pyridoxal 5'-phosphate dependent decarboxylation with inversion of configuration

Asada¹,

Tanizawa²,

Sawada³

et al. 1981

Biochemistry

View full text Add to dashboard Cite

show abstract

“…Very little detail is available concerning the AdoMetDC reaction. By using tritiated water in enzymatic assays, a primary tritium isotope effect of 4.5 was observed (8). This high isotope effect indicates a significant proton exchange of an active-site residue with solvent.…”

mentioning

confidence: 98%

Role of Cysteine-82 in the Catalytic Mechanism of Human S-Adenosylmethionine Decarboxylase

1999

View full text Add to dashboard Cite

S-Adenosylmethionine decarboxylase is a pyruvate-dependent enzyme. The enzyme forms a Schiff base with substrate, S-adenosylmethionine, through the pyruvoyl moiety. This facilitates the release of CO2 from the substrate, which must then be protonated on the alpha carbon in order to permit hydrolysis of the Schiff base to release the product. The catalytic mechanism of human S-adenosylmethionine decarboxylase was investigated via mutagenic and kinetic approaches. The results of enzyme kinetic studies indicated that Cys-82 is a crucial residue for activity and this residue has a basic pKa. Iodoacetic acid inhibited wild-type enzyme activity in a time- and pH-dependent manner but did not affect the already reduced activity of mutant C82A. Reaction of this mutant with iodoacetic acid led to approximately one less mole of reagent being incorporated per mole of enzyme alphabeta dimer than with wild-type S-adenosylmethionine decarboxylase. Both wild-type and C82A mutant S-adenosylmethionine decarboxylases were inactivated by substrate-mediated transamination, but this reaction occurred much more frequently with C82A than with wild-type enzyme. A major proportion of the recombinant C82A mutant protein was in the transaminated form in which the pyruvoyl cofactor is converted into alanine. This suggests that incorrect protonation of the pyruvate, rather than the substrate, occurs much more readily when Cys-82 is altered. On the basis of these results, it was postulated that residue Cys-82 may be the proton donor of the decarboxylation reaction catalyzed by S-adenosylmethionine decarboxylase.

show abstract

“…Pyruvoyl-dependent enzymes generate this cofactor through an autoproteolytic cleavage into α and β subunits, leaving the pyruvate at the N-terminus of the α subunit (). The mechanism of decarboxylation by pyruvate-dependent enzymes has been best characterized for histidine decarboxylase from Lactobacillus ( , ) and Escherichia coli AdoMetDC ( − ). The reaction (Scheme ) begins with the substrate forming a Schiff base with the pyruvate cofactor (steps 1 and 2).…”

mentioning

confidence: 99%

Single-Turnover Kinetic Analysis of Trypanosoma cruzi S-Adenosylmethionine Decarboxylase

Kinch

Phillips

2000

Biochemistry

View full text Add to dashboard Cite

Trypanosoma cruzi S-adenosylmethionine decarboxylase (AdoMetDC) catalyzes the pyruvoyl-dependent decarboxylation of S-adenosylmethionine (AdoMet), which is an important step in the biosynthesis of polyamines. The time course of the AdoMetDC reaction under single-turnover conditions was measured to determine the rate of the slowest catalytic step up to and including decarboxylation. Analysis of this single-turnover data yields an apparent second-order rate constant for this reaction of 3300 M(-1) s(-1) in the presence of putrescine, which corresponds to a catalytic rate of >6 s(-1). This rate is minimally 100-fold faster than the steady-state rate suggesting that product release, which includes Schiff base hydrolysis, limits the overall reaction. AdoMetDC exhibits an inverse solvent isotope effect on the single-turnover kinetics, and the pH profile predicts a pK(a) of 8.9 for the basic limb. These results are consistent with a Cys residue functioning as a general acid in the rate-determining step of the single-turnover reaction. Mutation of Cys-82 to Ala reduces the rate of the single turnover reaction to 11 M(-1) s(-1) in the presence of putrescine. Further, a solvent isotope effect is not observed for the mutant enzyme. Reduction of the wild-type enzyme with cyanoborohydride traps the Schiff base between the enzyme and decarboxylated substrate, while little Schiff base species of either substrate or product was trapped with the C82A mutant. These data suggest that Cys-82 functions as a general acid/base to catalyze Schiff base formation and hydrolysis. The solvent isotope and pH effects are mirrored in single-turnover analysis of reactions without the putrescine activator, yielding an apparent second-order rate constant of 150 M(-1) s(-1). The presence of putrescine increases the single-turnover rate by 20-fold, while it has relatively little effect on the affinity of the enzyme for product. Therefore, putrescine likely activates the T. cruzi AdoMetDC enzyme by accelerating the rate of Schiff base exchange.

show abstract

Stereochemistry and kinetic isotope effects in the decarboxylation of S-adenosylmethionine catalyzed by the pyruvyl enzyme, S-adenosylmethionine decarboxylase.

Cited by 21 publications

References 43 publications

Stereochemistry of meso-.alpha.,.epsilon.-diaminopimelate decarboxylase reaction: the first evidence for pyridoxal 5'-phosphate dependent decarboxylation with inversion of configuration

Stereochemistry of meso-.alpha.,.epsilon.-diaminopimelate decarboxylase reaction: the first evidence for pyridoxal 5'-phosphate dependent decarboxylation with inversion of configuration

Role of Cysteine-82 in the Catalytic Mechanism of Human S-Adenosylmethionine Decarboxylase

Single-Turnover Kinetic Analysis of Trypanosoma cruzi S-Adenosylmethionine Decarboxylase

Contact Info

Product

Resources

About