Premium
Evidence for PQQ as cofactor in 3,4‐dihydroxyphenylalanine (dopa) decarboxylase of pig kidney
Author(s) -
Groen Barend W.,
van der Meer Robert A.,
Duine Joannis 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)80179-0
Subject(s) - pyrroloquinoline quinone , cofactor , enzyme , chemistry , dihydroxyphenylalanine , biochemistry , pyridoxal phosphate , aromatic l amino acid decarboxylase , pyridoxal , stereochemistry , biology , neuroscience , dopamine
Pig kidney 3,4‐dihydroxyphenylalanine (dopa) decarboxylase (EC 4.1.1.28) was purified to homogeneity. Treatment of the enzyme with phenylhydrazine (PH) according to a procedure developed for analysis of quinoproteins gave products which were identified as the hydrazone of pyridoxal phosphate (PLP) and the C(5)‐hydrazone of pyrroloquinoline quinone (PQQ). This method failed, however, in quantifying the amounts of cofactor. Direct hydrolysis of the enzyme by refluxing with hexanol and concentrated HCl led to detachment of PQQ from the protein in a quantity of 1 PQQ per enzyme molecule. In view of the reactivity of PQQ towards amines and amino acids, we postulate that it participates as a covalently bound cofactor in the catalytic cycle of the enzyme, in interplay with PLP. Since several other enzymes have been reported to show the atypical behaviour of dopa decarboxylase, it seems that the PLP‐containing group of enzymes can be subdivided into pyridoxoproteins and pyridoxo‐quinoproteins.