IS 23] 



KLOTZ — NITROGEN METABOLISM IN FUNGI 



315 



theoretical curve for auto catalysis. The relation of ammonia 

 production to carbohydrate present was further shown by the 

 culture of A. niger on media containing varying percentages of 

 asparagin and the same concentration of sugar. On media 

 having 0.5, 1.0, and 2.5 per cent asparagin the organism after 

 reaching its maximum growth (in about 3 days) rapidly decom- 

 posed the amide-amino acid into ammonia nitrogen ; on the other 

 hand, where only little asparagin was present and the amount of 

 sugar remained the same, that is, relatively large in comparison, 

 little or no ammonia was produced and the amount of NH,.N 

 simply decreased. 



Making further use of the van Slyke "micro" method for amino 

 N, Waksman ('IS) made a study of the proteolytic enzymes of sev- 

 eral soil fungi, Aspergillus niger being employed in most of the 

 work. He showed that Penicillium chrysogenum and Actinomyces 

 sp. 101, which had been found to favor the production of more 

 amino than ammonia N when grown in a peptone solution, 

 produced strongly proteolytic enzymes, whereas the organisms, 

 as several species of Aspergillus, which produced more am- 

 monia than amino N, formed weaker enzymes. Compared 

 with the proteolytic enzymes of animal origin, the fungous en- 

 zymes were found to differ in being less limited by hydrion 

 concentration (P H values were not determined; reactions were 

 indicated by litmus and phenolphthalein), by having a lower 

 optimum temperature, by not being precipitated by safranin, 

 and in being able to pass a Pasteur-Chamberland filter. In its 

 production of enzymes Aspergillus niger was not influenced by 

 the sugar content of the medium. The activity of both exo- 

 and endo-proteoclastic enzymes produced by the fungi in peptone- 

 containing media was greater than that of the enzymes produced 

 in nutrients containing no peptone. The fast-growing Asper- 

 gillus niger produced its most active enzymes during the first 3 

 days of incubation, whereas the slower-growing A. ochraceus in- 

 creased in proteoclastic activity up to the eighteenth day of in- 

 cubation, after which there was a decline. He attempted an 

 explanation on the grounds that A . niger, reaching its maximum 

 growth in about 3 days, during this time necessarily produced 

 strongly acting enzymes and also acids, which acted injuriously 



