P450 11a1 cholesterol side chain cleaving enzyme at C20-C22 for pregnenolone synthesys. Pregnenolone is formed via three sequential monooxygenation reactions that involve the progressive production of 22R-hydroxycholesterol (22HC) and 20alpha,22R-dihydroxycholesterol, followed by the cleavage of the C20-C22 bond. the 2.5-Å crystal structure of CYP11A1 in complex with the first reaction intermediate, 22HC. The axial ligand at the fifth coordination site of the heme iron(III) is provided by the sulfide S- of Cys423 in 46a1. Coordination of the heme iron by ionic donor acceptor bond Fe3+-S- plays a central role in singlet oxygen bonding scission at the sixth coordination site on the heme iron(III). Back to the tutorial.

Transfere Grafic File 3MZS22OHcholestJBC10.tgf Integrated Scientific Information System deposit DATA:

The four pyrol rings of the porphyrine are serrounding by nitrogen atoms the central irone(III).
The four methyl groups -CH3 and two vinyl groups >C= -CH2 support hydrophobic accommodation of heme interior and active saite substrate .
Back to the tutorial