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Binding behaviour of substrate analogous spin‐labelled n ‐alkylamines in liver microsomal cytochrome P ‐450
Author(s) -
Pirrwitz J.,
Lassman G.,
Rein H.,
Ristau O.,
Jänig G.R.,
Ruckpaul K.
Publication year - 1977
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(77)80631-5
Subject(s) - chemistry , humanities , philosophy
The binding affinity of alkylamines (type II substrates) to cytochrome P-450 from liver microsomes increases with elongation of the alkyl side chain [l] . These investigations revealed that hydrophobic interactions determine the binding properties not only of type I substrates but also of type II substrates. By spin labelling of such a homologous series it is possible to obtain detailed structural information about the local environment of the bound substrates. Whereas in [l] only the optically active binding of the substrates was analysed, it is possible by the use of spin labelled substrates, moreover, to determine the bound as well as the free substrate molecules in titration experiments. Although type II substrate analogous spin labels as SL-metyrapone bound to bacterial [2] as well as to liver microsomal cytochrome P-450 [3] were studied, the number of binding sites was not determined. In this study a homologous series of SL-n-alkylamines with varying length of the alkyl side chain (m = 1, 2,7, 10) [4] (see fig.1) was investigated with the aim to get local structural data of bound substrates of different chain length and to determine the number of binding sites in microsomal cytochrome P-450. The following pertinent findings were shown: The SL-n-alkylamine with m = 10 was rigidly bound to P-450 indicating a well accessible large binding area.