PMSF

Metabolism of nafamostat, a clinically used serine protease inhibitor, was investigated with human blood and liver enzyme sources. All the enzyme sources examined (whole blood, erythrocytes, plasma and liver microsomes) showed nafamostat hydrolytic activity. V(max) and K(m) values for the nafamostat hydrolysis in erythrocytes were 278 nmol/min/mL blood fraction and 628 microM; those in plasma were 160 nmol/min/mL blood fraction and 8890 microM, respectively. Human liver microsomes exhibited a V(max) value of 26.9 nmol/min/mg protein and a K(m) value of 1790 microM. Hydrolytic activity of the erythrocytes and plasma was inhibited by 5, 5'-dithiobis(2-nitrobenzoic acid), an arylesterase inhibitor, in a concentration-dependent manner. In contrast, little or no suppression of these activities was seen with phenylmethylsulfonyl fluoride (PMSF), diisopropyl fluorophosphate (DFP), bis(p-nitrophenyl)phosphate (BNPP), BW284C51 and ethopropazine. The liver microsomal activity was markedly inhibited by PMSF, DFP and BNPP, indicating that carboxylesterase was involved in the nafamostat hydrolysis. Human carboxylesterase 2 expressed in COS-1 cells was capable of hydrolyzing nafamostat at 10 and 100 microM, whereas recombinant carboxylesterase 1 showed significant activity only at a higher substrate concentration (100 microM).

Yeast was grown in glucose- or galactose-containing media without or with proteinase inhibitors, phenylmethanesulphonyl fluoride and pepstatin. Culture growth was practically not affected by these compounds. Yeast growth on glucose in the presence of either phenylmethanesulphonyl fluoride or pepstatin entails accumulation of cytochromes c, c1, b and aa3 to a 25--30% excess above the control by the stationary phase, while cell respiration is unaffected. During growth on galactose the maximal cytochrome content (per unit weight of biomass) is reached in the mid-exponential phase and then decreases by 30--40% towards the stationary phase, while cell respiration remains constant. Addition of phenylmethanesulphonyl fluoride or pepstatin in the mid-exponential phase blocks the decrease in cytochrome levels and has no effect on cell respiration. Mitochondrial populations isolated from stationary-phase control and phenylmethanesulphonyl fluoride-grown cells glucose cultures display identical succinate oxidase and partial-respiratory-chain activities, despite the differences in cytochrome contents. However, the activities of individual respiratory complexes measured after maximal activation are nearly proportional to the amounts of corresponding components.

The purpose of this study was to isolate, purify and optimize the production conditions of an organic solvent tolerant and thermostable lipase from Acinetobacter sp. AU07 isolated from distillery waste. The lipase production was optimized by response surface methodology, and a maximum production of 14.5U/mL was observed at 30°C and pH 7, using a 0.5% (v/v) inoculum, 2% (v/v) castor oil (inducer), and agitation 150rpm. The optimized conditions from the shake flask experiments were validated in a 3L lab scale bioreactor, and the lipase production increased to 48U/mL. The enzyme was purified by ammonium sulfate precipitation and ion exchange chromatography and the overall yield was 36%. SDS-PAGE indicated a molecular weight of 45kDa for the purified protein, and Matrix assisted laser desorption/ionization time of flight analysis of the purified lipase showed sequence similarity with GDSL family of lipases. The optimum temperature and pH for activity of the enzyme was found to be 50°C and 8.0, respectively. The lipase was completely inhibited by phenylmethylsulfonyl fluoride but minimal inhibition was observed when incubated with ethylenediaminetetraacetic acid and dithiothreitol. The enzyme was stable in the presence of non-polar hydrophobic solvents.