Esterases and Lipases 34" 



Esterases and Lipases 



These terms are used in reference to enzymes which hydrolyze esters 

 of carboxylic acids. There is an overlapping between enzyme types and 

 some seem to occupy intermediate positions between Hpases and ester- 

 ases, and react like both forms. {Chessick, 1953; Gomori, 19'^2) Broadly 

 speaking, esters of short-chained fatty acids are acted on by esterases, 

 long-chained esters by lipases. 



Esterases or lipases are not destroyed by acetone fixation, are resistant 

 to heat and can be embedded in paraffin if not used excessively (3 hours, 

 maximtun, 58 °C). They can be incubated with the long-chained fatty 

 acid esters of sorbitan and mannitan, water-soluble commercial prod- 

 ucts by the name of "Tween." On hydrolysis, the liberated fatty acids 

 form insoluble calcium soaps deposited at the sites. These are converted 

 into lead soaps and then into brown sulfide of lead. 



Esters of naphthols also are tised and naphthol is liberated and dem- 

 onstrated by azo-cotipling. 



Esterase, Azo-Coupling (gomori, 1953) 



fixation: cold acetone, parafTin embedding, page 339. 



solutions: 



Barbital buffer: 



sodium diethyl barbiturate (10.3 gm./500 ml. 



water) 66.5 ml. 



0.1 M HCl 33.5 ml. 



Shake and filter. 



Substrate: 



dissolve a or t'-naphthylacetate 10.0 mg. 



in acetone 1.0 ml, 



add to solution of: 



fl-naphthyl diazonium naphthalene-l,5-disulfo- 



nate 40.0 mg. 



2M NaCI 50.0 ml. 



barbital buffer, pH 7.8 20.0 ml. 



distilled water 29.0 ml. 



procedure: 



1. Xylene, 2 changes: 3 minutes each. 



2. Absolute acetone: 1 miniue. 



