Structure of ACC synthase inactivated by the mechanism-based inhibitor L-vinylglycine.
L-Vinylglycine (L-VG) is both a substrate for and a mechanism-based inhibitor of 1-aminocyclopropane-1-carboxylate (ACC) synthase. The ratio of the rate constants for catalytic conversion to alpha-ketobutyrate and ammonia to inactivation is 500/1. The crystal structure of the covalent adduct of the inactivated enzyme was determined at 2.25 Angstroms resolution. The active site contains an external aldimine of the adduct of L-VG with the pyridoxal 5'-phosphate cofactor. The side chain gamma-carbon of L-VG is covalently bound to the epsilon-amino group of Lys273. This species corresponds to one of the two alternatives proposed by Feng and Kirsch [Feng, L. and Kirsch, J.F. (2000) L-Vinylglycine is an alternative substrate as well as a mechanism-based inhibitor of 1-aminocyclopropane-1-carboxylate synthase. Biochemistry 39, 2436-2444] and presumably results from Michael addition to a vinylglycine ketimine intermediate.
Capitani
Guido
G
Biochemisches Institut der Universität Zürich, Switzerland. capitani@bioc.unizh.ch
Tschopp
Markus
M
Eliot
Andrew C
AC
Kirsch
Jack F
JF
Grütter
Markus G
MG
D018360:Crystallography, X-Ray; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D008190:Lyases / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000378:metabolism; D027845:Malus / Q000201:enzymology; D008958:Models, Molecular; D015394:Molecular Structure; D017434:Protein Structure, Tertiary; D011732:Pyridoxal Phosphate / Q000494:pharmacology; D013379:Substrate Specificity
D004791:Enzyme Inhibitors; C006507:vinylglycine; D011732:Pyridoxal Phosphate; D008190:Lyases; C021773:1-aminocyclopropanecarboxylate synthase; D005998:Glycine