ABSTRACT
Prostaglandin F (PGF) ethanolamide (prostamide F) synthase, which catalyzed the reduction of prostamide H(2) to prostamide F(2alpha), was found in mouse and swine brain. The enzyme was purified from swine brain, and its amino acid sequence was defined. The mouse enzyme consisted of a 603-bp open reading frame coding for a 201-amino acid polypeptide with a molecular weight of 21,669. The amino acid sequence placed the enzyme in the thioredoxin-like superfamily with Cys(44) being the active site. The enzyme expressed in Escherichia coli as well as the native enzyme catalyzed not only the reduction of prostamide H(2) to prostamide F(2alpha) but also that of PGH(2) to PGF(2alpha). The V(max) and K(m) values for prostamide H(2) were about 0.25 micromol/min.mg of protein and 7.6 microm, respectively, and those for PGH(2) were about 0.69 micromol/min.mg of protein and 6.9 microm, respectively. Neither PGE(2) nor PGD(2) served as a substrate for this synthase. Based on these data, we named the enzyme prostamide/PGF synthase. Although the enzyme showed a broad specificity for reductants, reduced thioredoxin preferentially served as a reducing equivalent donor for this enzyme. Moreover, Northern and Western blot analyses in addition to the prostamide F synthase activity showed that the enzyme was mainly distributed in the brain and spinal cord, and the immunohistochemical study in the spinal cord showed that the enzyme was found mainly in the cytosol. These results suggest that prostamide/PGF synthase may play an important functional role in the central nervous system.
Subject(s)
Hydroxyprostaglandin Dehydrogenases/genetics , Thioredoxins/genetics , Amino Acid Sequence , Animals , Brain/enzymology , Conserved Sequence , Cytosol/enzymology , Dinoprostone/analogs & derivatives , Dinoprostone/metabolism , Female , Humans , Hydroxyprostaglandin Dehydrogenases/classification , Hydroxyprostaglandin Dehydrogenases/metabolism , Kinetics , Male , Mice , Mice, Inbred C57BL , Molecular Sequence Data , Polymerase Chain Reaction , Species Specificity , Substrate Specificity , Swine , Thioredoxins/classification , Thioredoxins/metabolismABSTRACT
Prostaglandin (PG) D(2) ethanolamide (prostamide D(2)) was reduced to 9alpha,11beta-PGF(2) ethanolamide (9alpha,11beta-prostamide F(2)) by PGF synthase, which also catalyzes the reduction of PGH(2) and PGD(2) to PGF(2alpha) and 9alpha,11beta-PGF(2), respectively. These enzyme activities were measured by a new method, the liquid chromatographic-electrospray ionization-mass spectrometry (LC/ESI/MS) technique, which could simultaneously detect the substrate and all products. PGF(2alpha), 9alpha,11beta-PGF(2), PGD(2), PGH(2), 9alpha,11beta-prostamide F(2), and prostamide D(2) were separated on a TSKgel ODS 80Ts column, ionized by electrospray, and detected in the negative mode. Selected ion monitoring (SIM) of m/z 353 ([M-H](-)), 353 ([M-H](-)), 351 ([M-H](-)), 333 ([M-H-H(2)O](-)), 456 ([M+59](-)), and m/z 358 ([M-37](-)) was used for quantifying PGF(2alpha), 9alpha,11beta-PGF(2), PGD(2), PGH(2), 9alpha,11beta-prostamide F(2), and prostamide D(2), respectively. The detection limit for PGF(2alpha) and 9alpha,11beta-PGF(2) was 0.01pmol; that for PGH(2) and PGD(2), 0.1pmol; and that for prostamide D(2) and 9alpha,11beta-prostamide F(2), 0.5 and 0.03pmol, respectively. The LC/ESI/MS technique for measuring PGF synthase activity showed higher sensitivity than other methods. Using this method, we found that Bimatoprost, the ethyl amide analog of 17-phenyl-trinor PGF(2alpha) and an anti-glaucoma agent, inhibited all three reductase activities of PGF synthase when used at a low concentration. These results suggest that Bimatoprost also behaves as a potent PGF synthase inhibitor in addition to having prostamide-like activity.
Subject(s)
Chromatography, Liquid/methods , Hydroxyprostaglandin Dehydrogenases/chemistry , Lipids/chemistry , Prostaglandin D2/chemistry , Prostaglandins F, Synthetic/chemical synthesis , Spectrometry, Mass, Electrospray Ionization/methods , Amides , Bimatoprost , Cloprostenol/analogs & derivatives , Enzyme Inhibitors/chemistry , Enzyme Stability , Humans , Hydroxyprostaglandin Dehydrogenases/antagonists & inhibitors , Recombinant Proteins/chemistry , Recombinant Proteins/isolation & purification , Restriction Mapping , Substrate SpecificityABSTRACT
The amino acid sequence of membrane-associated prostaglandin (PG) E synthase-2 (mPGE synthase-2), which has a broad specificity in its thiol requirement for a catalytic activity, has the consensus region from 104Leu to 120Leu found in glutaredoxin and of thioredoxin. The sequence of Cys-x-x-Cys in the consensus region is the active site for thioredoxin and mPGE synthase-2 also has this amino acid sequence (110Cys-x-x-113Cys). The mutation from 110Cys to Ser or the double mutation from 110Cys and 113Cys to Ser caused loss of PGE synthase activity, whereas the single mutation from 113Cys to Ser did not affect the enzyme activity. These results indicate that 110Cys, but not 113Cys, is the essential amino acid in the active site of mPGE synthase-2. 110Cys is an important amino acid in PGE synthase activity and plays the critical role as Cys at the same position in redoxin. Moreover, we found that the reduced form of lipoic acid (dihydrolipoic acid) serves as one of the natural activators of mPGE synthase-2 in the cells.
Subject(s)
Cysteine/chemistry , Intramolecular Oxidoreductases/chemistry , Oxidoreductases , Thioctic Acid/analogs & derivatives , Amino Acid Sequence , Binding Sites , Catalytic Domain , Dithiothreitol/pharmacology , Dose-Response Relationship, Drug , Glutaredoxins , Humans , Kinetics , Leucine/chemistry , Molecular Sequence Data , Mutagenesis, Site-Directed , Mutation , Oxidation-Reduction , Oxidative Stress , Prostaglandin-E Synthases , Protein Binding , Protein Structure, Tertiary , Proteins/chemistry , Serine/chemistry , Thioctic Acid/chemistry , Thioredoxins/chemistryABSTRACT
The ice-nucleating bacterium Pantoea ananas KUIN-3 accumulated glucose in cells following a shift in temperature (10 degrees C) from the optimum growth temperature (30 degrees C). This accumulation might be caused by the activation of glucose-6-phosphatase. Although this strain after culturing at 30 degrees C was harmed by freezing, the cryotolerance of this strain was reached about 80% after cold acclimation at 10 degrees C.
