Metabolism; Digestion and Translocation 271 



widely distributed in both higher and lower plants. Both 

 these and the diastases are most important in the produc- 

 tion of malt used in brewing and distilling. The diastases 

 are also important medicinally as an aid to amylose diges- 

 tion, and manjr patented forms are on the market. 



Another enzyme of special interest requiring further 

 stud}^ is pectase, a form important in the hydrolysis of a 

 portion of the cell-wall, producing a jelly from the pectic 

 compounds. 



157. Protein enzymes. Protein enzymes were among 

 the first to receive attention, and they have been more 

 completely studied in the animal organism, where the 

 action of pepsin in the stomach and that of trypsin 

 received into the intestine from the pancreas are well under- 

 stood. These enzymes must occur in plants, or else 

 others which serve the same purpose. 



Through ferments many proteins are converted into the 

 more diffusible proteoses and peptones; while tryptic 

 ferments may give a more complete digestion, reducing 

 the peptone to the readily diffusible amido and amino 

 acids, such as leucin and asparagin. Ferments which 

 have been regarded as tryptic have been known for some 

 time in plants, such as papain from the papaw, and bro- 

 melin from the pineapple. From recent work it appears 

 that some of the so-called tryptic ferments may be, in fact, 

 combinations of peptic and ereptic ferments. The last- 

 named class is found by Vines to be well distributed in 

 plants, and it decomposes the peptones with the pro- 

 duction of amido and amino acids. 



Doubtless many of the protein enzymes in plants are 

 intracellular. The carnivorous plants, such as the sun- 



