Esterases acetone powder

Enantioselective enzymatic ester hydrolyses of prochiral trimethylsilyl-substituted diesters of the malonate type have been applied for the synthesis of the related optically active monoesters68. As an example of this particular type of biotransformation, the enantioselective conversion of the diester 82 is illustrated in Scheme 17. Hydrolysis of compound 82 in phosphate buffer, catalyzed by porcine liver esterase (PLE E.C. 3.1.1.1) or horse liver acetonic powder (HLAP), gave the optically active monoester 83 (absolute configuration not reported) in 86% and 49% yield, respectively. The enantiomeric purities... 

Acetone Powder Containing Esterase Activity. The main advantage in using crude homogenates or acetone powders of organs such as liver is to have a cheap source of different enzymes. If one of these is desired for a specific substrate, the crude enzymatic mixture can be used with some advantage, compared to the purified enzymes. Pig liver acetone powder (PLAP), together with other extracts, is commercially available or can be prepared from fresh pig liver. PLAP has been used for the enantioselective hydrolysis of the racemic acetate of rrans-2-phenylcyclohexanol... 

The acetates of 1-arylalkan-l-ols were successfully resolved by acetone powders (PLAP and goat liver acetone powder, GLAP) containing esterase activity (eq 12). ... 

An interesting application of the esterase activity of horse liver acetone powder (HLE) has been the enantioselective hydrolysis of racemic lactones. The powder proved to be more effective than PLE in this hydrolysis, from which the unreacted lactone was recovered with high enantiomeric excess. The process seems more effective for S and medium size lactones (eq 13). ... 

The use of ester hydrolase preparations such as pig liver esterase (PLE) or pig liver acetone powder (PLAPy complements reduction approaches for the synthesis of enantio-enriched alcohols. 

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). 

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. 

Choline acetylase may also be extracted from powder of acetone-dried brain. In these preparations choline esterase is destroyed to a large extent. Sometimes the destruction of choline esterase is neatly complete. In this way the two enzymes may be separated (Nachmansohn and John, 111)... 

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