Crystal structures of 1-aminocyclopropane-1-carboxylate (ACC) synthase in complex with aminoethoxyvinylglycine and pyridoxal-5'-phosphate provide new insight into catalytic mechanisms.
The structures of tomato 1-aminocyclopropane-1-carboxylate synthase (ACS) in complex with either cofactor pyridoxal-5'-phosphate (PLP) or both PLP and inhibitor aminoethoxyvinylglycine have been determined by x-ray crystallography. The structures showed good conservation of the catalytic residues, suggesting a similar catalytic mechanism for ACS and other PLP-dependent enzymes. However, the proximity of Tyr152 to the C-gamma-S bond of model substrate S-adenosylmethionine implies its critical role in the catalysis. The concerted accomplishment of catalysis by cofactor PLP and a protein residue, as proposed on the basis of the ACS structures in this paper, may represent a general scheme for the diversity of PLP-dependent catalyses. PLP-dependent enzymes have been categorized into four types of folds. A structural comparison revealed that a core fragment of ACS in fold type I is superimposable over tryptophan synthase beta subunit in fold type II and mouse ornithine decarboxylase in fold type III, thus suggesting a divergent evolution of PLP-dependent enzymes.
Huai
Q
Q
Department of Biochemistry and Biophysics and Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, 27599-7260, USA.
Xia
Y
Y
Chen
Y
Y
Callahan
B
B
Li
N
N
Ke
H
H
D000595:Amino Acid Sequence; D002384:Catalysis; D018360:Crystallography, X-Ray; D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry*; D008190:Lyases / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011732:Pyridoxal Phosphate / Q000737:chemistry*
D011732:Pyridoxal Phosphate; D008190:Lyases; C021773:1-aminocyclopropanecarboxylate synthase; C088137:aminoethoxyvinylglycine; D005998:Glycine