The Milk Lipase System. II. Effect of Formaldehyde
1956; Elsevier BV; Volume: 39; Issue: 10 Linguagem: Inglês
10.3168/jds.s0022-0302(56)94862-7
ISSN1529-9066
AutoresDaniel P. Schwartz, I.A. Gould, W.J. Harper,
Tópico(s)Diet, Metabolism, and Disease
ResumoSome investigators believe that the enzyme system of milk contains more than one lipase.The effect of formaldehyde on milk lipase activity at various pH levels and times of incubation tends to substantiate this belief.Editor.Various investigators have expressed concern about the sensitivity of the milk lipase system to added formaldehyde (1,2,5,6,8).The results reported in the literature when formaldehyde has been used in milk lipase studies have not always been in agreement.The differences may be explained in part by nonuniformity of procedures used in respect to concentration of formaldehyde, incubation conditions, and methods of measuring the results.Herrington and Krukovsky (2) found that lipolytic activity in 20% normal raw cream was reduced approximately 70% by addition of formaldehyde, irrespective of the concentratiou of formaldehyde employed.These workers therefore postulated the possible existence in milk of two lipases, one being sensitive and the other tolerant to added formaldehyde.Roahen and Sommer (6) obtained similar results with formaldehyde.However, according to Tarassuk and Richardson (8), the addition of formaldehyde to milk followed by aging resulted in no loss of lipolytic activity.Peterson et al. ( 5) reported that formaldehyde inhibited the action of milk lipase on tributyrin by 75% at pH 8.5 during a 30-minute incubation period.Gould (1) found formaldehyde to be ineffective as an inhib.itor of lipase activity in homogenized cream.Murray (4), studying the effect of various substances on the velocity of fat hydrolysis by pancreatic ]ipase, observed that aldehydes and ketones markedly inhibited the enzyme.By converting the ketone to the corresponding oxime, he was able to nullify the inhibitory power of the compound.This led him to postulate that a specific affinity exists between the carbonyl oxygen and the active centers of the lipase molecule.The experiments of Weinstein and Wynne (9) supported Murray's hypothesis that pancreatic lipase contains essential chemical groups which react or complex with the carbonyl group of ketones and aldehydes.These investigators also
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