REACTION SPECIFICITY OF PYRIDOXAL PHOSPHATE ENZYMES

  • Toney, Michael D, (PI)

Project: Research project

Description

DESCRIPTION:Pyridoxal phosphate (PLP) dependent enzymes are ubiquitous in nitrogen metabolism and catalyze many medically important transformations. As a group, they catalyze an extraordinarily wide variety of reactions, and a fundamental, unresolved question that bears on the design of enzyme inhibitors is how a given apoenzyme determines a unique reaction specificity. Dialkylglycine decarboxylase (DGD) is an unusual PLP dependent enzyme that rapidly catalyzes both decarboxylation and transamination in its normal catalytic cycle, thereby providing a vehicle for incisive studies on the control of enzymatic reaction specificity. High resolution X-ray structures for DGD are available, and reveal two alkali metal ion-specific binding sites. One, near the active site, is responsible for the activating effects of large (K+, Rb+) and inhibitory effects of small (Na+, Li+) ions. The elucidation of the mechanisms by which DGD discriminates between and is catalytically controlled by alkali metals has very broad physiological significance. DGD is structurally representative of a medically important class of aminotransferases capable of acting alternately on primary amines and alpha-amino acids. The specific aims of this project are to test the hypotheses that: 1) C-C (decarboxylation) and C-H (transamination) bond cleavage occur via a single substrate binding subsite in the DGD active site, which activates these bonds by large stereoelectronic effects; 2) DGD specifically catalyzes oxidative vs. non-oxidative decarboxylation by proceeding through a concerted transition state in which CO2 loss and proton transfer occur simultaneously; 3) Active site structural changes in Ser80 and Tyr301 caused by exchange of activating for inhibitory ions control catalytic activity; 4) The ability of several aminotransferases to act in alternative half-reactions on primary amines and alpha-amino acids is largely determined by two active site residues, Glu215 and Va1244.
StatusFinished
Effective start/end date5/1/977/31/13

Funding

  • National Institutes of Health: $280,128.00
  • National Institutes of Health
  • National Institutes of Health: $192,858.00
  • National Institutes of Health: $31,896.00
  • National Institutes of Health: $185,626.00
  • National Institutes of Health: $287,535.00
  • National Institutes of Health: $304,997.00
  • National Institutes of Health
  • National Institutes of Health: $305,520.00
  • National Institutes of Health: $287,210.00
  • National Institutes of Health: $307,710.00
  • National Institutes of Health: $64,612.00
  • National Institutes of Health
  • National Institutes of Health: $315,646.00
  • National Institutes of Health
  • National Institutes of Health: $352,568.00
  • National Institutes of Health: $311,938.00

Fingerprint

2,2-dialkylglycine decarboxylase
Pyridoxal Phosphate
Enzymes
Alanine Racemase
Alkali Metals
Apoenzymes
Proton transfer
Transaminases
Metabolism
Nitrogen
Metal ions
Ions
Amines
Free energy
Bearings (structural)
Racemases and Epimerases
Amino Acids
Binding Sites
Protonation
Biosynthesis

Keywords

  • Medicine(all)
  • Biochemistry, Genetics and Molecular Biology(all)