98
D.C. Hill et al.
Eosinophilic leukocytes accumulate in blood and tissue in many allergic and
inflammatory reactions. Sonicates of eosinophils express three to eight times as
much lysophospholipase (Lyso PL) activity as comparable numbers of neutrophils or mononuclear leukocytes. Lyso PL catalyses the hydrolysis of fatty
acid ester bonds of lysophospholipids, liberating the corresponding free fatty
acid and glycerophosphate.
Partially purified Lyso PL from bovine liver was incubated with 1-palmitoyl
lysophosophatidylcholine (Lyso PC) and Lyso PC-Epalmitoyl-l-14C]. After
stopping the reaction, the product was separated with heptane and measured
radiometrically. This assay was used in the detection, isolation and characterisation of cyclooctatin (Fig. 6), a diterpene metabolite of Streptomyces melanosporofaciens [103, 104]. Cyclooctatin is a competitive inhibitor of Lyso PL. This
compound was also slightly active against PLA2 and Phospholipase C (PLC).
Cyclooctatin had low toxicity when tested in vivo.
4.1.3 Human Leukocyte Elastase Inhibitors
Human leukocyte elastase (HLE) is one of the most destructive enzymes known.
This enzyme hydrolyses several connective tissue components, including elastin,
proteoglycan and certain types of collagen. Release of HLE from PMNL by
inflammatory stimuli may play a role in destructive processes associated with
chronic inflammatory diseases. HLE activity was measured by monitoring the
release of p-nitroaniline from methoxysuccinyl-(Ala)2-Pro-Val-p-nitroanilide.
The effects of inhibitors on other proteinases were measured using other
p-nitroanilide substrates. This assay was used in the discovery of FR901277,
a peptidic metabolite of Streptomyces resistomycificus [105], and FR901451,
a tricyclic depsipeptide produced by a Flexibacter sp. [106, 107].
FR901277 inhibited HLE, porcine pancreatic elastase (PPE) and chymotrypsin but was only a weak inhibitor of trypsin. 0d-Antitrypsin (alAT), an
endogenous serine proteinase inhibitor, inhibited all enzymes tested. FR901277
was a competitive HLE inhibitor, and moderated HLE-induced paw edema in
mice. FR901451 was also shown to be a competitive HLE inhibitor, and to have
promising activity in an in vivo model based on elastase induced changes of
respiratory mechanics in hamsters.
4.2 Cancer
4.2.1 Inhibition of Cell Signalling Enzymes
Ras poteins, which are localized on the inner side of the plasma membrane, are
important in signal transduction. The interaction of these proteins with the
plasma membrane requires post-translational modification of their carboxyterminus. All ras proteins share a common sequence, the CAAX box which
D.C. Hill et al.
Eosinophilic leukocytes accumulate in blood and tissue in many allergic and
inflammatory reactions. Sonicates of eosinophils express three to eight times as
much lysophospholipase (Lyso PL) activity as comparable numbers of neutrophils or mononuclear leukocytes. Lyso PL catalyses the hydrolysis of fatty
acid ester bonds of lysophospholipids, liberating the corresponding free fatty
acid and glycerophosphate.
Partially purified Lyso PL from bovine liver was incubated with 1-palmitoyl
lysophosophatidylcholine (Lyso PC) and Lyso PC-Epalmitoyl-l-14C]. After
stopping the reaction, the product was separated with heptane and measured
radiometrically. This assay was used in the detection, isolation and characterisation of cyclooctatin (Fig. 6), a diterpene metabolite of Streptomyces melanosporofaciens [103, 104]. Cyclooctatin is a competitive inhibitor of Lyso PL. This
compound was also slightly active against PLA2 and Phospholipase C (PLC).
Cyclooctatin had low toxicity when tested in vivo.
4.1.3 Human Leukocyte Elastase Inhibitors
Human leukocyte elastase (HLE) is one of the most destructive enzymes known.
This enzyme hydrolyses several connective tissue components, including elastin,
proteoglycan and certain types of collagen. Release of HLE from PMNL by
inflammatory stimuli may play a role in destructive processes associated with
chronic inflammatory diseases. HLE activity was measured by monitoring the
release of p-nitroaniline from methoxysuccinyl-(Ala)2-Pro-Val-p-nitroanilide.
The effects of inhibitors on other proteinases were measured using other
p-nitroanilide substrates. This assay was used in the discovery of FR901277,
a peptidic metabolite of Streptomyces resistomycificus [105], and FR901451,
a tricyclic depsipeptide produced by a Flexibacter sp. [106, 107].
FR901277 inhibited HLE, porcine pancreatic elastase (PPE) and chymotrypsin but was only a weak inhibitor of trypsin. 0d-Antitrypsin (alAT), an
endogenous serine proteinase inhibitor, inhibited all enzymes tested. FR901277
was a competitive HLE inhibitor, and moderated HLE-induced paw edema in
mice. FR901451 was also shown to be a competitive HLE inhibitor, and to have
promising activity in an in vivo model based on elastase induced changes of
respiratory mechanics in hamsters.
4.2 Cancer
4.2.1 Inhibition of Cell Signalling Enzymes
Ras poteins, which are localized on the inner side of the plasma membrane, are
important in signal transduction. The interaction of these proteins with the
plasma membrane requires post-translational modification of their carboxyterminus. All ras proteins share a common sequence, the CAAX box which