Conference paper

Evidence of the Existence of a High Spin Low Spin Equilibrium in Liver Microsomal Cytochrome P450, and its Role in the Enzymatic Mechanism

H. Rein ; Department of Biocatalysis, C'entral Institute of Molecular Biology, Academy of Sciences of the GDR 1115 Berlin, GDR
O. Ristau ; Department of Biocatalysis, C'entral Institute of Molecular Biology, Academy of Sciences of the GDR 1115 Berlin, GDR
J. Friedrich ; Department of Biocatalysis, C'entral Institute of Molecular Biology, Academy of Sciences of the GDR 1115 Berlin, GDR
G.-R. Janig ; Department of Biocatalysis, C'entral Institute of Molecular Biology, Academy of Sciences of the GDR 1115 Berlin, GDR
K. Ruckpaul ; Department of Biocatalysis, C'entral Institute of Molecular Biology, Academy of Sciences of the GDR 1115 Berlin, GDR

Abstract

In rabbit liver microsomal cytochrome P450 a high spin (S =
= 5/2) low spin (S = 1/2) equilibrium has been proved to exist by
recording temperature difference spectra in the Soret and in the
visible region of the absorption spectrum of solubilized cytochrome
P450. In the presence of type II substrates the predominantly low
spin state of cytochrome P450 is maintained, only a very small shift
to lower spin is observed. Ligands of the heme iron, such as cyanide
and imidazole, pr9duce a pure low spin state and therefore in the
presence of these ligands no temperature difference spectra can be
obtained. In the presence of type I substrate, however, the spin
equilibrium is shifted to the high spin state. The extent of this
shift (1) depends on specific properties of the substrate and (2) it is
generally relatively small, up to about 80/o in the case of substrates
investigated so far.

Keywords

Hrčak ID:

196364

URI

https://hrcak.srce.hr/196364

Publication date:

30.3.1977.

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