Hydroxy-prostaglandin dehydrogenase

This enzyme [EC 1.1.1.50], also referred to as hydroxy-prostaglandin dehydrogenase, catalyzes the reaction of androsterone with NAD(P)+ to produce 5a-androstane-3,17-dione and NAD(P)H. Other 3a-hydroxysteroids can act as substrates as well as 9-, 11- and 15-hydroxy-prostaglandins. The stereochemistry is B-specific with respect to the pyridine coenzymes. 

Besides 12-LOX in platelets, the 5-LOX isoforms are constitutive in neutrophils. Evidences indicate that LOXs are involved in inflammation diseases and in atherosclerosis. 5-LOX is the enzyme that catalyzes the formation of leukotrienes with potential role for leukocytes and platelets interaction and inflammation. After platelet and leukocyte stimulation, products of both COX-1 and 5-LOX pathways increase. COX-1 activity derivatives increase the vascular permeability mediated by prostaglandins and produce platelet aggregation mediated by TXA2. The product of the lipoxygenase pathway, 5-oxo-6,8,1 1,14-eicosatetraenoic acid (5-Oxo-ETE), induces leukocyte chemotaxis and inflammation. 5-Oxo-ETE is formed by the oxidation of 5S-hydroxy-ETE (5-HETE) by 5-hydroxyeicosanoid dehydrogenase (5-HEDH), a microsomal enzyme found in leukocytes and platelets (42). 

The reverse reaction has also been noted, i.e. the formation of PGE compounds from prostaglandins of the F series. This reaction is catalysed by an enzyme different from the 9-keto reductase, prostaglandin 9-hydroxy dehydrogenase [325-327], In vivo, this reaction may take place to a considerable extent in certain species, for example the rat and the guinea pig [281], whereas it seems to be of minor importance in others, such as the human [274,280,281]. 

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