DESIGN OF AN ARTIFICIAL HEMOPROTEIN BASED ON HUMAN SERUM-ALBUMIN

For modelling cytochrome P450-catalyzed reactions, an artificial hemop rotein was designed. Upon complex formation of human serum albumin wit h iron protoporphyrine IX, there occurred the incorporation of heme in to the protein and formation of a specific complex with the albumin to heme molar ratio 2:1. The apparent dissociation constant K-d of the c omplex, as determined by optical absorption spectroscopic technique, w as 1.9+/-0.4 M(-6). Based on spectral studies and molecular modelling of the complex spatial structure, it was assumed that His 31 or His 90 may be the most probable 5th ligand for the heme iron. The artificial hemoprotein was able to catalyze (in the presence of riboflavin as el ectron carrier) the NADH-dependent aniline hydroxylation and dimethyla niline and amidopyrine N-demethylation. The electron transfer pathway from NADH to substrate was demonstrated. Flavin appears to serve as an input center (mediator) for the rapid transfer of electrons from NADH to heme, where substrate is oxidized. The same reactions were accompl ished using riboflavin photoreduction in the hemoalbumin - riboflavin system with the unfocussed laser emission at lambda=457.9 nm. As elect ron donor, metallic zinc was used. The artificial hemoprotein obtained was also able to catalyze H2O2-dependent oxidase reactions.