Domain architecture of the heme-independent yeast cystathionine beta-synthase provides insights into mechanisms of catalysis and regulation.
Biochemistry
; 39(34): 10548-56, 2000 Aug 29.
Article
in En
| MEDLINE
| ID: mdl-10956046
ABSTRACT
Cystathionine beta-synthase from yeast (Saccharomyces cerevisiae) provides a model system for understanding some of the effects of disease-causing mutations in the human enzyme. The mutations, which lead to accumulation of L-homocysteine, are linked to homocystinuria and cardiovascular diseases. Here we characterize the domain architecture of the heme-independent yeast cystathionine beta-synthase. Our finding that the homogeneous recombinant truncated enzyme (residues 1-353) is catalytically active and binds pyridoxal phosphate stoichiometrically establishes that the N-terminal residues 1-353 compose a catalytic domain. Removal of the C-terminal residues 354-507 increases the specific activity and alters the steady-state kinetic parameters including the K(d) for pyridoxal phosphate, suggesting that the C-terminal residues 354-507 compose a regulatory domain. The yeast enzyme, unlike the human enzyme, is not activated by S-adenosyl-L-methionine. The truncated yeast enzyme is a dimer, whereas the full-length enzyme is a mixture of tetramer and octamer, suggesting that the C-terminal domain plays a role in the interaction of the subunits to form higher oligomeric structures. The N-terminal catalytic domain is more stable and less prone to aggregate than full-length enzyme and is thus potentially more suitable for structure determination by X-ray crystallography. Comparisons of the yeast and human enzymes reveal significant differences in catalytic and regulatory properties.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Saccharomyces cerevisiae
/
Cystathionine beta-Synthase
Type of study:
Prognostic_studies
Limits:
Humans
Language:
En
Journal:
Biochemistry
Year:
2000
Document type:
Article
Affiliation country:
United States