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Dopamine β‐hydroxylase from bovine adrenal medulla contains covalently‐bound pyrroloquinoline quinone
Author(s) -
van der Meer Robert A.,
Jongejan Jacob A.,
Duine Johannis A.
Publication year - 1988
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(88)80838-x
Subject(s) - pyrroloquinoline quinone , adrenal medulla , dopamine , chemistry , medulla , dopamine beta monooxygenase , covalent bond , tyrosine hydroxylase , biochemistry , endocrinology , enzyme , catecholamine , biology , cofactor , organic chemistry
Treatment of homogeneous dopamine β‐hydroxylase (DBH) preparations from bovine adrenals with the inhibitor phenylhydrazine (PH) changed the structureless absorption spectrum of DBH into spectra with a maximum at 350 nm. A product with this absorption spectrum could be detached with pronase, enabling its isolation. It appeared to be the C(5) hydrazone of pyrroloquinoline quinone (PQQ) and PH, as judged from its properties and the fact that it could be transformed into PQQ itself. From the yield obtained a ratio of 0.85 PQQ per enzyme subunit was calculated. In contrast to copper‐quinoprotein amine oxidases (EC 1.4.3.6), hydrazone formation in DBH did not require saturation of the mixture with O 2 . DBH is the first copper‐quinoprotein hydroxylase found so far. The implications of this finding for the current views on mechanism of action and inhibition by hydrazines are discussed. The success of the recently developed ‘hydrazine method’ [(1987) FEBS Lett. 221, 299‐304] for all different types of amine oxidoreductases, suggest that the method could also be applied to other enzymes for which hydrazines are inhibitors and where the identity of the cofactors has not been established or the presence of PQQ is suspected.