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F. LIPMANN, L. C. TUTTLE 



VOL. 4 (1950) 



Table III shows the pjj optimum of the Hpase reaction to be at 7.2. The measure- 

 ments at the more acid range, however, do not give a true impression of the pn depend- 

 ence. A decrease of activity here is partly caused by the higher concentrations of free 

 fatty acid which is rather strongly inhibitory^. 



TABLE III 



THE Ph OPTIMUM OF HYDROXAMIC ACID FORMATION WITH PORK LIVER EXTRACT 



Each tube contained 0.25 ml liver extract, o.i ml of o.i M octanoate, and 0.15 ml of 2 M hydroxy 1- 

 amine hydrochloride-NaOH buffer, 60 minute incubated at 37°. The buffer was prepared by 

 neutralizing a 4 M hydroxylamine HCl solution with increasing amounts of NaOH and adjusting 

 the volume with water 



In Table IV, the activity of some lipase inhibitors is recorded. Like lipase the 

 hydroxamic acid reaction is strongly inhibited by fluoride^" and hexyl resorcinoF. The 

 action of benzoate is of some interest. An inhibitory effect of benzoate on the oxidation 

 of butyric but none or less of octanoic acid was observed by Quastel and his colla- 

 borators^^. The hydroxamic acid reaction follows the same pattern of decreased inhibi- 

 tion with increasing chain length of the fatty acids. The inhibition of hydrolytic lipase 

 action of this liver extract was checked manometrically with tributyrin in bicarbonate 

 solution. It was found to a similar extent to be affected by fluoride and hexyl resorcinol; 

 but benzoate showed only a small inhibition of about 10%. 



TABLE IV 



ACTION OF LIPASE INHIBITORS ON HYDROXAMIC ACID FORMATION WITH HOG LIVER EXTRACTS 



In Table V, the lipase action and hydroxamic acid formation are compared with 

 the various fractions, obtained as described above from hog liver extract. The parallel 

 is rather striking. It may be noted that the absolute activity expressed in /uM turnover 



References p. jog. 



