Naslov
The Cation−π Interaction between Lys53 and the Flavin of Fructosamine Oxidase (FAOX-II) Is Critical for Activity

Autori
Collard, Franҫois ; Fagan, Rebecca L. ; Zhang, Jianye ; Nemet, Ina ; Palfey, Bruce A. ; Monnier, Vincent M.

Izvornik
Biochemistry (0006-2960) 50 (2011), 37; 7977-7986

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
fructosamine oxidase; oxidative deglycation; fructosamine; Amadori products

Sažetak
Fructosamine oxidases (FAOXs) are flavincontaining enzymes that catalyze the oxidative deglycation of low molecular weight fructosamines or Amadori products. The fructosamine substrate is oxidized by the !avin in the reductive half-reaction, and the reduced flavin is then oxidized by molecular oxygen in the oxidative half-reaction. The crystal structure of FAOX-II from Aspergillus fumigatus reveals a unique interaction between Lys53 and the isoalloxazine. The ammonium nitrogen of the lysine is in contact with and nearly centered over the aromatic ring of the flavin on the si-face. Here, we investigate the importance of this unique interaction on the reactions catalyzed by FAOX by studying both half-reactions of the wild-type and Lys53 mutant enzymes. The positive charge of Lys53 is critical for flavin reduction but plays very little role in the reaction with molecular oxygen. The conservative mutation of Lys53 to arginine had minor efects on catalysis. However, removing the charge by replacing Lys53 with methionine caused more than a million-fold decrease in flavin reduction, while only slowing the oxygen reaction by 30-fold.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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