Structure and function correlations between the rat liver threonine deaminase and aminotransferases.
The rat liver threonine deaminase is a cytoplasmic enzyme that catalyses the pyridoxal-phosphate-dependent dehydrative deamination of L-threonine and L-serine to ammonia and alpha-ketobutyrate and pyruvate, respectively, in vivo. During deamination, a molecule of the cofactor is converted to pyridoxamine phosphate. Recently, the ability of this enzyme to accomplish an inverse half-reaction, restoring pyridoxal-phosphate and L-alanine or L-aminobutyrate, respectively, from pyruvate or 2-oxobutyrate, was reported. In order to investigate the molecular mechanisms of this transaminating activity, a molecular model of rat liver threonine deaminase was constructed on the basis of sequence homology with the biosynthetic threonine deaminase of Escherichia coli, the crystal structure of which is known. The model has structural features shared by aminotransferases, suggesting that tertiary structural elements may be responsible for the transaminating activity observed for rat liver threonine deaminase.
Scarselli
Maria
M
Biomolecular Structure Research Center, University of Siena, Italy.
Padula
Maria Giuseppina
MG
Bernini
Andrea
A
Spiga
Ottavia
O
Ciutti
Arianna
A
Leoncini
Roberto
R
Vannoni
Daniela
D
Marinello
Enrico
E
Niccolai
Neri
N
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D003593:Cytoplasm / Q000201:enzymology; D008099:Liver / Q000201:enzymology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D051381:Rats; D016415:Sequence Alignment; D013329:Structure-Activity Relationship; D013913:Threonine Dehydratase / Q000737:chemistry / Q000378:metabolism*; D000637:Transaminases / Q000737:chemistry / Q000378:metabolism*
D000637:Transaminases; D013913:Threonine Dehydratase