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Croatica Chemica Acta, Vol. 48 No. 1, 1976.

Original scientific paper

Hepatic Cytochrome P-450. A Proton Magnetic Relaxation Study of Microsomal, Solubilized and Partially Reconstituted Enzyme System

K. Ruckpaul ; Research Centre of Molecular Biology, Academy of Sciences of the G.D. R., Berlin, G. D. R.
S. Maričić ; Institute of Immunology, 41000 Zagreb, Rockefellerova 2, Yugoslavia
G.-R. Janig ; Research Centre of Molecular Biology, Academy of Sciences of the G.D. R., Berlin, G. D. R.
B. Benko ; Institute of Immunology, 41000 Zagreb, Rockefellerova 2, Yugoslavia
S. Vuk-Pavlović ; Institute of Immunology, 41000 Zagreb, Rockefellerova 2, Yugoslavia
H. Rein ; Research Centre of Molecular Biology, Academy of Sciences of the G.D. R., Berlin, G. D. R.

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Abstract

The longitudiJ:ial proton magnetic relaxation times, Ti, were
measured from -5 to 40 °c for microsomal, solubilized and reconstituted
cytochrome P-450 obtained from phenobarbital-induced rat
livers. The paramagnetic contribution to the rates was derived by
subtraction of the rates measured on dithionite-CO-reduced samples.
The same values were obtained for microsomal P-450 on
reduction with NADPH. PMR titratio.n by KCN yielded a dissociation
constant of about 30 mM. This is three orders of magnitude larger
than for metmyoglobin. It is concluded that the measured PMR
rates are most likely due to the P-450 (and P-420) haem-iron while
the 300/o non-haem iron found in both the microsomal and s olubilized
P-450 is .ineffective for the PMR rates. These rates increase
several times on isotopic dilution (D20 for H20) with the microsomes
and diminish for the solubilized samples. Microsomes show 170/o
residual, encaged, H20. Most of their paramagnetic PMR rate is due
to the parama.gnetic iron located on the outside of microsomes.
This is demonstrated by measurements with deuterated samples to
which 190/o H20 had been added. Hence, the solubilized P-450 is
homogeneous regarding PMR, but the microsomes are not.

Keywords

Hrčak ID:

196492

URI

https://hrcak.srce.hr/196492

Publication date:

20.2.1976.

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