title: Structural and enzyme activity studies demonstrate that aryl substituted 2,3-butadienamine analogs inactivate Arthrobacter globiformis amine oxidase (AGAO) by chemical derivatization of the 2,4,5-trihydroxyphenylalanine quinone (TPQ) cofactor.
abstract: Copper amine oxidases (CAOs) are a family of redox active enzymes containing a 2,4,5-trihydroxyphenylalanine quinone (TPQ) cofactor generated from post translational modification of an active site tyrosine residue. The Arthrobacter globiformis amine oxidase (AGAO) has been widely used as a model to guide the design and development of selective inhibitors of CAOs. In this study, two aryl 2,3-butadienamine analogs, racemic 5-phenoxy-2,3-pentadienylamine (POPDA) and racemic 6-phenyl-2,3-hexadienylamine (PHDA), were synthesized and evaluated as mechanism-based inactivators of AGAO. Crystal structures show that both compounds form a covalent adduct with the amino group of the substrate-reduced TPQ, and that the chemical structures of the rac-PHDA and rac-POPDA modified TPQ differ by the allenic carbon that is attached to the cofactor. A chemical mechanism accounting for the formation of the respective TPQ derivative is proposed. Under steady-state conditions, no recovery of enzyme activity is detected when AGAO pre-treated with rac-PHDA or rac-POPDA is diluted with excess amount of the benzylamine substrate (100-fold K(m)). Comparing the IC(50) values further reveals that the phenoxy substituent in POPDA offers an approximately 4-fold increase in inhibition potency, which can be attributed to a favourable binding interaction between the oxygen atom in the phenoxy group and the active site of AGAO as revealed by crystallographic studies. This hypothesis is corroborated by the observed >3-fold higher partition ratio of PHDA compared to POPDA. Taken together, the results presented in this study reveal the mechanism by which aryl 2,3-butadienamines act as mechanism-based inhibitors of AGAO, and the potency of enzyme inactivation could be fine-tuned by optimizing binding interaction between the aryl substituent and the enzyme active site.
authors.affiliation: School of Molecular Bioscience, The University of Sydney, NSW 2006, Australia.
authors.forename: Karin
authors.initials: K
authors.lastname: Ernberg
authors.forename: Bo
authors.initials: B
authors.lastname: Zhong
authors.forename: Kristin
authors.initials: K
authors.lastname: Ko
authors.forename: Larry
authors.initials: L
authors.lastname: Miller
authors.forename: Yen Hoang le
authors.initials: YH
authors.lastname: Nguyen
authors.forename: Lawrence M
authors.initials: LM
authors.lastname: Sayre
authors.forename: J Mitchell
authors.initials: JM
authors.lastname: Guss
authors.forename: Irene
authors.initials: I
authors.lastname: Lee
mesh_terms: D006631:Amine Oxidase (Copper-Containing) / Q000037:antagonists & inhibitors*; D000588:Amines / Q000737:chemistry* / Q000494:pharmacology*; D001173:Arthrobacter / Q000201:enzymology*; D003067:Coenzymes / Q000737:chemistry*; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives* / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure
chemical_list: C086758:2,4,5-trihydroxyphenylalanine quinone; D000588:Amines; D003067:Coenzymes; D004295:Dihydroxyphenylalanine; D006631:Amine Oxidase (Copper-Containing)