J. Biol. Chem., Vol. 264, Issue 14, 7850-7855, May, 1989
Inhibition of prolyl hydroxylase by poly(ADP-ribose) and phosphoribosyl- AMP. Possible role of ADP-ribosylation in intracellular prolyl hydroxylase regulation
MZ Hussain, QP Ghani and TK Hunt
Department of Stomatology, School of Dentistry, University of California, San Francisco 94143.
Poly(ADP-ribose) prepared by incubating NAD+ with rat liver nuclei
inhibited the hydroxylation reaction catalyzed by purified prolyl
hydroxylase (proline,2-oxoglutarate dioxygenase, EC 1.14.11.2) in vitro.
Near complete inhibition of the enzyme was seen in the presence of 6 nM
(ADP-Rib)18 with a Ki(app) of 1.5 nM. The monomer unit of poly(ADP-ribose),
adenosine diphosphoribose (ADP-Rib), was found to be a weak inhibitor. On
the other hand, poly(ADP-ribose)-derived phosphoribosyl-AMP (PRib-AMP) and
its dephosphorylated product, ribosyl- ribosyl-adenine (Rib-RibA),
inhibited the enzyme in nanomolar concentrations (Ki(app) 16.25 nM). The
order of inhibition was (ADP- Rib)18 greater than PRib-AMP, Rib-RibA much
greater than ADP-Rib. These results suggested that the 1"----2'
ribosyl-ribosyl moiety in these compounds was involved in the inhibition of
the enzyme. The possibility that intracellular prolyl hydroxylase is
regulated by the involvement of ADP-ribosylation reactions was examined in
confluent cultures of skin fibroblast treated with 20 mM lactate. The
activity of prolyl hydroxylase was stimulated by 145% over that of
untreated cultures. In the lactate-treated cells, the level of NAD+ was
lowered and the total ADP-ribosylation of cellular proteins reduced by 40%.
These observations imply that the lactate-induced activation of cellular
prolyl hydroxylase is mediated by a reduction in ADP-ribosylation and that
the synthesis and degradation of ADP-ribose moiety(ies) may possibly
regulate prolyl hydroxylase activity in vivo.