ENZYMES 509 



papaya, Ficus carica, Cucumis utilissimus, Ananassa sativa, &c. ' According to 

 Neumeister 2 many of the higher plants never produce any proteolytic enzymes, and 

 hence the latter do not seem to be essential in proteid metabolism, although a 

 certain amount of peptone appears to be formed in those seeds (barley, poppy, 

 beetroot, maize, &c.) in which pepsin appears during germination. No pepsin can, 

 however, be detected in lupins, peas, rye, oats, &c., and the slight amount of peptone 

 which appears in these plants, and which is in some cases deposited in the seeds, 

 must arise as a product of vital metabolism, just as amides do. 



The enzyme of most bacteria is, like trypsin, active only in an alkaline or 

 neutral solution, and this is in correlation with the fact that putrefactive bacteria 

 commonly exist in neutral or alkaline media 3 . On the other hand, the enzyme of 

 Nepenthes, Drosera, &c. acts only in the presence of acid. The papain of latex 

 is active chiefly in alkaline and neutral solutions, but perhaps also in faintly acid 

 solutions 4 , while the proteolytic ferment of Penicillium seems to be still less 

 influenced by the presence of acid 5 . Plants evidently produce several different 

 kinds of proteolytic enzymes, but direct experiments are required to show whether 

 vegetable-pepsins produce peptone with albumoses as intermediate products, 

 whether vegetable-trypsins carry the digestion as far as the formation of leucin, 

 tyrosin, &c., and whether only the latter ferments are able to digest nucleins 6 . 



A rennet ferment that coagulates milk is produced by certain bacteria and 

 many of the higher plants, but its importance is as yet unknown. Literature : 

 Fliigge, I.e., p. 209; Lafar, 1. c., p. 209; Green, Annals of Botany, 1893, Vol. vn, 

 p. 112 ; Bruhne, Beitr. z. Physiol. u. Morphol. v. Zopf, 1894, iv, p. 27. 



\_Oxidase enzymes. The best known of these is the laccase first described by 

 Yoshida 7 , which induces the oxidation of the sap of Rhus into black lacquer 

 varnish when in contact with air. It also exerts a similar oxidizing action upon 

 hydroquinone, pyrogallol, and many polyphenols. The ferment acts best at about 

 20 C. but is not destroyed by heating to 70 C. 8 Manganese appears to be \ 



1 Cf. Hansen, Arb. d. Bot. Inst. in Wurzburg, 1887, Bd. ill, p. 266; Green, Annals of Botany, 



1893, Vol. vn, p. 107. 



2 Neumeister, Zeitschr. f. Biologic, 1894, Bd. XXX, p. 447. The older literature is mentioned 

 here. On the occurrence of peptones cf. also E. Schultze, Journ. f. Landw., 1881, Bd. XXIX, p. 285 ; 

 Versuchsst, 1882, Bd. xxvn, p. 358 ; Journ. f. prakt. Chemie, 1885, Bd. XXXII, p. 449 ; Frankfurt, 

 Versuchsst., 1896, Bd. XLVII, p. 466 Reinke, Unters. a. d. Bot. Lab. in Gottingen, 1881, Heft 2, 

 p. 52 (Aethaliuiti}. 



3 Fermi, Centralbl. f. Bact., 1891, Bd. X, p. 404. Cf. also Fliigge; Lafar, 1. c. According to 

 Hjort (Centralbl. f. Physiol., 1896, Bd. X, p. 192), Agaricus ostreatus and Polyporus sulphureus 

 contain a similar ferment. 



* Cf. Neumeister, Physiol. Chemie, 1893, I, p. 192; Sharp, Chem. Centralbl., 1894, I, p. 512. 

 The enzyme of Aethalium seems to have similar properties. Cf. Celakovsky, Flora, Erg.-bd., 1892, 



* Hansen, Flora, 1889, p. 88; Bruhne (Zopfs Beitrage, 1894, I, p. 26) for Hormodendron. 



Cf. Neumeister, Physiol. Chemie, I, pp. 107, 129, 187, 200. On the differences between animal 

 pepsins, see Wroblewski, Zeitschr. f. physiol. Chemie, 1895, Bd. xxi, p. 18; Popoff, ibid., 1894, 



^YosMdffchemistry of Lacquer, Journal of the Chemical Society, 1883, Vol. XLIII, p. 47*- 



* Bertrand, Compt. rend., 1894, T. cxvm, p. 1215 ; 1895, T. cxx, p. 266; Bull. Soc. C 



1894, T. n, p. 717; Yoshida, 1. c. 



