Pw. Schindler et al., IDENTIFICATION OF 2 NEW INHIBITORS OF THE HEPATIC GLUCOSE-6-PHOSPHATASE SYSTEM, Drug development research, 44(1), 1998, pp. 34-40
A high-throughput screening assay aimed at the detection of inhibitors
of the translocase components of the hepatic glucose-6-phosphatase (G
6Pase) system was set up in a microplate Format using untreated and Tr
iton X-100(TM)-disrupted rat liver microsomes. The assay measured the
phosphate released from glucose-6-phosphate (G6P) using a standard cal
orimetric method. Mie identified two struct urally unrelated compounds
, 2-hydroxy-5-nitrobenzaldehyde and chlorogenic acid, which inhibited
the hydrolysis of G6P in untreated microsomes, each with IC50 values o
f 338 mu M and 226 mu M, respectively, but were devoid of activity in
disrupted microsomes. Thus, the two compounds exhibited a high degree
of specificity for translocase components. The effects of 2-hydroxy-5-
nitrobenzaldehyde bear a resemblance to the effects of pyridoxal phosp
hate. Studies with compounds structurally related to 2-hydroxy-5-nitro
benzaldehyde suggest that both a phenolic OH-group in ortho position t
o the aldehyde group and a suitable electron-withdrawing group in posi
tion 3 or 5 of the aromatic ring are indispensable for the activity of
this class of inhibitors. The inhibition pattern of chlorogenic acid
is distinct from that of phloretin and is dependent on a free carboxyl
group. The products of chlorogenic acid hydrolysis, quinic acid and c
affeic acid, are inactive. 2-Hydroxy-5-nitrobenzaldehyde type inhibito
rs and chlorogenic acid are potent new inhibitors for investigating th
e structure and function of the translocase components of the G6Pase s
ystem. (C) 1998 Wiley-Liss, Inc.