Human alpha-thrombin with high clotting activity and its proteolyzed derivative gamma-thrombin with virtually no clotting activity reacted in an essentially identical manner with antithrombin. The two enzyme forms bound proflavin with similar constants and showed identical behavior with small substrates. No significant differences were found for the antithrombin reactions (measured by proflavin displacement or active site titration) with respect to kinetics, extent of reaction, or effect of added heparin. The enzyme--antithrombin complexes could not be dissociated with sodium dodecyl sulfate (NaDodSO4) but the NaDodSO4-denatured complexes were dissociated by hydroxylamine treatment. The gamma-thrombin-antithrombin complex has an approximate molecular weight of 75 000 by disc gel electrophoresis as compared with 100 000 for the alpha-complex, consistent with the polypeptide structures of the two proteins. The gamma-thrombin--antithrombin complex did not inhibit clotting catalyzed by alpha-thrombin. In addition, fibrinogen did not affect the reaction of gamma-thrombin with antithrombin or antithrombin--heparin. Thus, the antithrombin and antithrombin--heparin reactions do not involve the fibrinogen recognition sites which are destroyed by proteolytic conversion of alpha-thrombin to the noncoagulant gamma form.

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Penicillin amidohydrolase [EC 3.5.1.11] was used to resolve stereoisomers of a β-amino acid ester (ethyl 3-amino-5-(trimethylsilyl)-4-pentynoate) by phenylacetylation. After screening commercially available sources of the immobilized enzyme, one was found to be significantly more efficient, and this was developed at 1-L scale reaction. The effects of phenylacetic acid concentration, β-amino acid ester concentration, and pH on bioconversion rates and side reactions were examined. The enzymatic reaction was monitored off-line by naphthoylation of samples and chiral analytical chromatography. The best conditions for the bioconversion were pH 5.7, 28 °C, and 14 000 units of enzyme activity per liter. The phenylacetic acid concentration was set at 50 g/L (0.37 M), and the amine at 100 g/L (0.47 M). Under these conditions, yields of the desired (S)amino acid ester were on the order of 90% with ee's of 95% or greater in less than 12 h. This process, along with a slight modification, was tested through 15 cycles at 0.4-L scale, and was scaled to 70 L. Recycle results extrapolated to approximately 25 reaction cycles before the enzyme lost 50% of its initial activity. Through three runs at 70 L, overall yield of (S)-amine was 42.7 ( 0.6%, overall yield of (R)-phenylacetyl amide was 47.2 ( 1.8%. The average ee of the amine (two runs) was 98.1 ( 0.4%, for the amide the ee was 99.5 ( 0.2%. Experimental Section I. Analytical. ReVersed Phase (RP-HPLC) Chromatography. Aqueous samples for RP-chromatography were diluted into an equal volume of acetonitrile, except for amine

Gluconobacter oxydans has the unique ability to regioselectively and rapidly oxidize sorbitol and other erythro saccharides. In this report a new process is described by which N-butylglucamine is regioselectively oxidized by the organism. A large-scale process is described by which N-butylglucamine can be converted to an intermediate (6-deoxy-6-butylaminosorbose) which can be readily converted to N-butyldeoxynojirimycin by catalytic hydrogenation. The primary process variables of temperature, pH, and added acids and salts were investigated in laboratory bioreactors. Since degradation of the sorbose product was rapid above room temperature, significant enhancement of the selectivity was achieved by lowering the temperature at which the bioconversion was run. The optimum temperature for this conversion was 12−15 °C. The pH maximum of the bioconversion was 5.5−6.0. However, the small gain in rate relative to pH 5.0 was at least offset by the increase in degradation of the product at the higher pH. Nitrate salts of N-butylglucamine could replace chloride salts, but sulfate, acetate, and phosphate salts could not. Sulfate in particular led to inhibition of the conversion, while phosphate and acetate led to increased degradation. At temperatures in the range of 12−15 °C, pH of around 5.0 and substrate concentrations of 0.2 M, Gluconobacter oxydans catalyzed bioconversion to 6-deoxy-6-butylaminosorbose with yields approaching 95%. These conditions were used to scale this process to 5500-L scale.

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