On the deaminating enzyme of flesh-fly larvae.

THE production of ammonia as their main nitrogenous end-product by flesh-fly larvae is now well known. The mechanism of its production however is still obscure [Messer and McLellan, 1935]. Hobson [1931] for instance was unable to find any evidence of deamination of glycine at PH 6-8 by aqueous extracts of Lucilia sericata larvae. One of us [Brown, 1935] carried out the same experiment using larvae of Wohlfahrtia vigil on both glycine and tyrosine and varying the PH from 4-0 to 8-0 with entirely negative results. Some hope for the elucidation of this problem lay in an observation of Weinland [1908], who found that in his peptone brei of Calliphora tissue the reaction became definitely alkaline to litmus presumably owing to the production of ammonia. In the present communication the presence of a deaminating enzyme has been established and some of its properties and conditions of action have been determined. ANALYTICAL METHODS. Ammonia was determined by permutit adsorption and nesslerisation [Peters and Van Slyke, 1932]. In analysing solutions containing protein or its breakdown products the colour on nesslerisation was unsatisfactory owing to a strawyellow tinge which developed; this could be obviated by repeated washings of the permutit after ammonia adsorption or by substitution of permutit adsorption by aeration into 0-1N HCI. Amino-nitrogen was estimated by alcoholic titration [Willstiatter' and Waldschmidt-Leitz, 1921] using N/50 alcoholic NaOH with cresolphthalein as indicator. Protein-nitrogen was measured by precipitating the protein with trichloroacetic acid and determining the nitrogen in the washed precipitate using the technique described by Farber and Wynne [1935]. Uric acid was determined by the method of Benedict and Franke [v. Peters and Van Slyke, 1932]. The organisms used in this investigation were Lucilia sericata Mg. and Calliphora erythrocephala Mg., both flesh-flies of the same ecological habit. Notes on their laboratory breeding are published elsewhere [Brown, 1936, 2].