Castor bean acid lipase

Fig.l. Sequential reactions of castor bean acid lipase. 

Hydrolyzes fat (present in ester form, such as glycerides) yielding fatty acids and glycerol. Catalyzes digestion. Widely distributed in the plant world, also in molds, bacteria, milk and milk products, and in animal tissues, especially in the pancreas, [soln from castor beans H. Gibian in Ullmann s Encyklopadie der technischen Chemie, 3rd ed., vol. 7, 406 -407 (1956). Purification of pancreatic lipase March s-Mouren el al.. Arch, Biochem. Biophys. 83, 309 (1959), Review of milk lipases Chan dan, Shahani, J, Dairy Sri. 47, 471 (1964). Comprehensive reviews Wills, Ad van. Lipid Res. 3, 197-240 (1965) Desnuelle in The Enzymes vol, 7, P. D. Boyer, Ed. (Academic Press, New York, 3rd ed<> 1972) pp 575-616. 

Comparative investigations of the rates of hydrolysis of various natural triglycerides by pancreatic lipase have been carried out by several workers (257-260), As a general rule it is found that vegetable fats, such as coconut oil, palm oil, peanut oil, and rice bran oil, are hydrolyzed more rapidly than animal fats, such as beef fat or whale oil. These studies do not shed much light on the mode of action of lipase, but tend to support the often quoted view that unsaturated fatty acids are split off more readily than saturated acids they are useful when the nutritional values of natural fats are under consideration. Castor bean lipase hydrolyzes coconut oil more rapidly than beef fat and certain other fats (261). 

Castor bean lipase is unusual in that its optimum pH is well to the acid side of neutrality values between 4.0 and 5.0 have generally been quoted 4.5 (J68), 4.85 ( 274), 4.7 (142, 275), and 4.0-4.2 (145), but the optimum pH was recently found to be 6.3 (146), This acid pH optimum is a special property of die lipase of ripe seeds, and the pH optimum of the lipase of the unripe castor bean or the plant itself lies between 8.5 and 10.5 (275). During germination, the optimum pH of the lipase changes from 4.7 to 6.8 (142). A similar phenomenon has been observed with cotton seeds, the pH optimum of the lipase increasing from 6.0 to... 

Activation effects have been described for other lipases. Thus milk lipase is stabilized and activated by glutathione and hydroquinone (330), serum lipase by sodium hexametaphosphate (331), tissue lipases by phosphate (332), and castor bean lipase is activated by strychnine (333) and by plant growth stimulants such as a-indolyl acetic acid and 2,4-dichlorophenoxyacetic acid (334). 

Castor bean lipase is inhibited by thiourea and formaldehyde, being more sensitive than pancreatic lipase to these agents (3.51), by sodium fluoride (363), and by chloral hydrate and urethan in high concentration (364). Plant growth hormones, such as 2,4-dichlorophenoxyacetic acid (365, 366), are stated to inhibit castor bean lipase, but have also been described as activators (334). 

However, generalization to include other oil seeds is not indicated, because lipases in other organelles must be involved in gluconeogenesis (see below). Involvement of the acid lipase in gluconeogenesis of castor bean has not been proven, and Muto and Bee vers (1974) have pointed out that the enzyme activity decreases before the peak of lipid breakdown in germinating castor beans. 

A concentrate with 83% 9-cis,ll-trans isomer was obtained from gentle dehydration of ricinoleic acid from castor bean oil and subsequent purification steps (4). The use of urea inclusion compounds does not seem to be a feasible procedure to separate 9-cis,l i-trans and l0-trans,l2-cis (23). Enzymes, however, are promising tools for these separations. A 98% concentrate of 9-cis,ll-trans was reported by using lipase from Geotrichum candidum. The enzyme was capable of esterifying selectively 9-cis, -trans to monohydric alcohols from a mixture of several isomers (24). A patent has been issued on purification and characterization of iso-merases from Propionibacterium acnes and Clostridium sporogenes. The purified isomerase preparations were able to quantitatively isomerize linoleic acid into the 10-trans,12-cis isomer of CLA (25). 

Connected with the controversial views on the origin of the oil bodies is the question as to whether they are bounded by membranes. Evidence for and against the existence of some kind of peripheral membrane is presented in Section 3.3.8. We should note, in addition, favourable evidence for an oil body membrane raised by the freeze-fracture studies on barley aleurone cells [20 b] and by biochemical analyses of peanut and walnut oil bodies which reveal phospholipid and protein characteristic of membranes. Finally, we should be aware that in addition to the possible existence of membrane protein, enzyme protein may also occur in oil bodies. Enzymes for fatty acid biosynthesis have been reported in oil bodies of developing castor bean [35] and for triglyceride hydrolysis (acid lipases) in the mature endosperm of this species the latter enzymes may not occur in oil bodies of other species (Chap. 6). 

Nevertheless, there are also reports, some of which are again based on the use of inhibitors, that certain enzymes involved in mobilization are not newly synthesized. The compound azetidine-2-carboxylic acid, an analogue of proline, does not stop isocitrate lyase increase in Cucurbita pepo or Cucumis sativus and it is therefore presumed that the enzyme existed in an inactive form before the chemical was applied [98]. Secondly, in some cases mobilization enzymes can be extracted from dry seeds (i.e. before germination) such as acid lipase in castor bean (see Fig. 6.8 [84]). Finally, it is thought that in some seeds trypsin-... 

The seed lipases from five plant species were selected because of their differences In the fatty acid composition of the storage trlacylglycerols. Castor bean contains about 80% rlclnolelc acid maize seed possesses about... 

CASTOR OIL An age-old home remedy seldom recommended now, castor oil (purge, NEOLOID, others) is derived from the bean of the castor plant, Ricinus communis, which contains two well-known noxious ingredients an extremely toxic protein, ricin, and an oil composed chiefly of the triglyceride of ricinoleic acid. The triglyceride is hydrolyzed in the small bowel by the action of lipases into glycerol and the active agent, ricinoleic acid, which acts primarily in the small intestine to stimulate secretion of fluid and electrolytes and speed intestinal transit. When taken on an empty stomach, as little as 4 mL of castor oil may produce a laxative effect within 1-3 hours however, the usual dose for a cathartic effect is 15-60 mL for adults. 

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