Cyclooxygenase (COX) is a key enzyme in the biosynthetic pathway lea
ding to the formation of prostaglan
dins, which are me
diators of inflammation [D.L. Dewitt, W.L. Smith, Primary structure of prostaglan
din G/H synthase from sheep vesicular glan
d determine
d from the complementary DNA sequence, Proc. Natl. Aca
d. Sci. USA 85 (1988) 1412–1416,
1]. It exists mainly in two isoforms COX-1 an
d COX-2 [A. Raz, A. Wyche, N. Siegel, P. Nee
dleman, Regulation of fibroblast cyclooxygenase synthesis by interleukin-1, J. Biol. Chem. 263 (1988) 3022–3028,
2]. The conventional non-steroi
dal anti-inflammatory
drugs (NSAIDs) have a
dverse gastrointestinal si
de-effects, because they inhibit both isoforms [T.D. Warner, F. Guiliano, I. Vojnovic, A. Bukasa, J.A. Mitchell, J.P. Vane, Nonsteroi
d drug selectivities for cyclo-oxygenase-1 rather than cyclo-oxygenase-2 are associate
d with human gastrointestinal toxicity: a full in vitro analysis, Proc. Natl. Aca
d. Sci. USA 96 (1999) 7563–7568,
3; L.J.
Marnett, A.S. Kalgutkar, Cyclooxygenase 2 inhibitors:
discovery, selectivity an
d the future, Tren
ds Pharmacol. Sci. 20 (1999) 465–469,
4; J.R. Vane, NSAIDs, Cox-2 inhibitors, an
d the gut, Lancet 346 (1995) 1105–1106,
5]. Therefore
drugs which selectively inhibit COX-2, known as coxibs were
develope
d. Recent reports on the harmful car
diovascular an
d renovascular si
de-effects of the anti-inflammatory
drugs have le
d to the quest for a novel class of COX-2 selective inhibitors. Keeping this in min
d, we have use
d the X-ray crystal structures of the complexes of the COX-1 an
d COX-2 with the known inhibitors for a rational, structure base
d approach to
design a small pepti
de, which is potent inhibitor for COX-2. The pepti
des have been checke
d experimentally by in-vitro kinetic stu
dies using surface plasmon resonance (SPR) an
d other biochemical metho
ds. We have i
dentifie
d a tripepti
de inhibitor which is a potential lea
d for a new class of COX-2 inhibitor. The
dissociation constant (
KD)
determine
d for COX-2 with pepti
de WCS is 1.90
d7; 10
−10 M, the kinetic constant (
Ki)
determine
d by spectrophotometry is 4.85
d7; 10
−9 M an
d the IC
50 value is 1.5
d7; 10
−8 M by ELISA test.