Bovine pancreas acetone powder

The catalyst for this reaction is the enzyme cholesterol esterase (EC 3.1.1.13). Bovine pancreas acetone powder (Sigma Chemical Company), a crude extract from pancreas. Is an inexpensive source of cholesterol esterase activity. This extract contains -15 units of cholesterol esterase activity/gram unit = pmol of ester... 

A very recent resolution method is the selective hydrolysis of the di-pentanoic acid ester of racemic binaphthol by cholesterol esterase in practice, inexpensive bovine pancreas acetone powder is used, which cleaves only the (Sl-ester42. 

In this two-step resolution, the enzyme catalyzes the hydrolysis of the diester to monoester, then the monoester to the diol. Each step contributes to the overall enantioselectivity. The reaction mixture is biphasic buffered water containing the cmde enzyme and an ether solution of the diester. The cmde enzyme is bovine pancreas acetone powder that contains many enz5mies, but the substrate rearts only with the cholesterol esterase so the other enzymes do not interfere, other than to make the work-up messy. The enz5mie cholesterol esterase requires a bile salt, taurocholate, for fiiU activity. This bile salt helps emulsify the two phases. Cholesterol esterase seems to behave more like a lipase than an esterase in this example since it works with the substrate in the organic phase. The dipentanoate ester is chosen to simplify the separation of starting diester and product diol (Figure 5.7). 

In a 12 L, round-bottomed flask equipped wdth an overhead stirrer, stir a two-phase mixture of an ether solution of binaphthol dipentanoate (4 L, 0.71 mol, prepared from 203 g of racemic binaphthol) and an aqueous solution of sodium taurocholate (60 g, cmde grade in 4 L of 0.1 M phosphate buffer, pH 7.5) to form an opaque emulsion. Add bovine pancreas acetone powder (150 g), stopper the flask to minimize evaporation of ether and continue stirring slowly. The pH of the emulsion is measured occasionally and readjusted to 7.2 + 0.3... 

Another example, with an even more obviously non-natural substrate, is shown in Figure 15.23. Chiral binaphthol has been widely used as an addend to promote enantiose-lective reactions, to prepare other chiral catalysts, and to design chiral ion receptors. In this example, a simple recrystallization of the ester, obtained in 92 % enantiomer excess, gave material with 99 % enantiomer excess. The enzyme is cholesterol esterase, but a crude and inexpensive form was used, bovine pancreas acetone powder. 

For preparative purposes, it is perhaps more convenient to start from pancreas acetone powder (pancreatin). Ninty-five per cent pure bovine procarboxypeptidase A has been obtained by ammonium sulfate fractionation of pancreatin extracts and isoelectric precipitations (47). When the proteins precipitated by 0.39 saturated ammonium sulfate are chromatographed on DEAE-cellulose in a concentration gradient of pH 8.0 phosphate buffer, the two last and most acidic peaks contain procarboxypeptidase A in an electrophoretically homogeneous form (48). The molecular weight of the protein determined by light scattering and sedimentation-diffusion is 94-96,000. Its isoelectric point in univalent buffers of 0.2 ionic strength is below 4.5. 

For many years a solution of crude acetone powder of bovine or porcine pancreas has been used to disaggregate tissues and to release cultured cells from their substratum. These preparations — referred to as trypsin 1 250 (based on an international standard) — contain not only trypsin but a range of enzymes including chymotrypsin and elastase which are equally important. Purified trypsin seldom is as efficient as the cruder preparations, especially on tissue disaggregation, when mucinous clumps result (Ronaldoni, 1959). 

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