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Prostacyclin (PGI2), a vascular protector with vasodilation and antithrombotic properties, is synthesized by coupling reactions of cyclooxygenase (COX, the first enzyme) with PGI2 synthase (PGIS, the second enzyme) using arachidonic acid (AA) as an initial substrate. The first COX product, prostaglandin H2 (PGH2) is also a command substrate for other prostanoid enzymes that produce distinct eicosanoids, such as thromboxane A2 (TXA2). The actions of TXA2 to cause vasoconstriction and platelet aggregation oppose the vasodilatory and anti-aggregatory effects of PGI2. Specifically upregulating PGI2 biosynthesis is an ideal model for the prevention and treatment of the TXA2-mediated thrombosis involved in strokes and myocardial infarctions. Here, we report that a single protein was constructed by linking COX-2 and PGIS together to form a new fusion enzyme through a transmembrane domain with 10 or 22 residues. The engineered protein expressed in HEK293 and COS-7 cells was able to continually convert AA to prostaglandin (PG) G2 (catalytic step 1), PGH2 (catalytic step 2), and PGI2 (catalytic step 3). The studies first demonstrate that a single protein with three catalytic functions could directly synthesize PGI2 from AA with a Km of approximately 3.2 microM. Specific upregulation of PGI2 biosynthesis through expression of the engineered single protein in the cells has shown strong activity in inhibiting platelet aggregation induced by AA in vitro, which creates a great potential for the fusion enzyme to be used as one of the new therapeutic interventions for strokes and heart attacks. The studies have also provided a model linking COX with its downstream enzymes to specifically regulate biosynthesis of eicosanoids which have potent biological functions.

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a b s t r a c tElectro-chemical mechanical polishing (ECMP), which combines anodic oxidation and soft abrasive polishing, was applied to single-crystal SiC. Ceria (CeO 2 ) slurry was used as an electrolyte for anodic oxidation as well as a polishing medium to remove the oxide layer. As a result of anodic oxidation, the surface hardness decreased from 34.5 GPa to 1.9 GPa, which made it possible to polish the oxidized SiC surface using a very soft abrasive such as CeO 2 . It was found that the material removal rate (MRR) of ECMP for a diamond-abrasive-polished surface was 3.62 μm/h. ECMP using CeO 2 slurry was conducted for 30 min on a diamond-abrasive-polished surface. All the scratches were completely removed and a smooth surface with a root mean square (RMS) roughness of 0.23 nm was obtained.

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