PGHS

Hershkovitz E and Poliak E 1997 Multidimensional generalization of the PGH turnover theory for activated rate processes J. Chem. Phys. 106 7678... 

Both methods suggest that the chemical structure of A A (cis double bonds connected by two single bonds) allows the fatty acid to access the cyclooxygenase active site of PGHS-1 through a narrow hydrophobic channel and to bind in a shape favorable for the cyclooxygenation reaction. 

The enzyme system responsible for the biosynthesis of PGs is widely distributed in mammalian tissues and has been extensively studied (2). It is referred to as prostaglandin H synthase (PGHS) and exhibits both cyclooxygenase and peroxidase activity. In addition to the classical PGs two other prostanoid products, thromboxane [57576-52-0] (TxA ) (3) and prostacyclin [35121 -78-9] (PGI2) (4) are also derived from the action of the enzyme system on arachidonic acid (Fig. 1). 

In order for the cyclooxygenase to function, a source of hydroperoxide (R—O—O—H) appears to be required. The hydroperoxide oxidizes a heme prosthetic group at the peroxidase active site of PGH synthase. This in turn leads to the oxidation of a tyrosine residue producing a tyrosine radical which is apparendy involved in the abstraction of the 13-pro-(5)-hydrogen of AA (25). The cyclooxygenase is inactivated during catalysis by the nonproductive breakdown of an active enzyme intermediate. This suicide inactivation occurs, on average, every 1400 catalytic turnovers. 

Fig. 3. Putative mechanism of PGH synthase action on arachidonic acid.

Prostaglandin Endoperoxides. The naturally occurring endoperoxides, PGG, PGG2, PGH, and PGH2, as well as a number of their... 

Earlier, the 9,11-etheno analog of PGHi, compound C, had been synthesized by the route shown below. It was found that this compound inhibits the PGH isomerase which forms PGEi but not the PGH reductase which catalyzes the formation of PGFiq (Ref. 6). 

Because the influence of gravitation pgh is negligible for horizontal (distribution) systems, this term is ignored in the equations. 

To measure the energy density in kWli/m , we relate the mass (m) to mass density (p) and volume (V) by m = pV. The potential energy may then be written as E = pVgH. Dividing both sides of E = rVgH by the volume produces E/V = pgH, which is... 

PGHS accomplishes two transformations, an initial reaction of arachidonic acid with 02 to yield PGG2 and a subsequent reduction of the hydroperoxide group (-OOH) to the alcohol PGH2- The sequence of steps involved in these transformations was shown in Figure 7.9, page 244. 

The production of carbon monoxide from trichloroflnoromethane catalyzed by cytochrome P450c nj proceeded through intermediate formation of the dichloroflnorocarbene (Li and Wackett 1993) (Fignre 7.70c). Other reactions included (3-elimination from l,l,l-trichloro-2,2,2-trifiuorethane (Fignre 7.70c). Pseudomonas putida strain G786 (pGH-2) was constructed to contain both the... 

Bjorge A. 2001. How persistent are marine mammal habitats in an ocean of variability In Evans PGH, Raga JA, editors. Marine mammals biology and conservation. New York (NY) Kluwer Academic/Plenum Publishers. 

PGF, PGH Prostaglandins F and H PGI2 Prostaglandin I2 also known as prostacyclin... 

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