152 THE CHEMISTRY OF THE PLANT 
Protein Group.—Con. 
Enzymes. 
Invertase 
Cytase 
the less complex, soluble, ‘di- 
alyzable Albumoses (to which 
the peptones belong). Other 
related groups are the Albu- 
minoids, some of which are 
crystallizable. All of these 
groups have innumerable 
forms differing from one 
another in solubility in acids, 
alkalies and salt solutions; in 
their coagulability with heat, 
salts, acids and alkalies and 
enzymes; in their power to 
dialyze, and in the forms of 
enzymes that can attack them 
and the forms of the pro- 
ducts of such enzymatic 
action. 
These are substances showing 
many of the characteristics of 
the protein compounds (e.g. 
destruction of activity by heat 
or salts of heavy metals, etc.), 
but not so complex. They are 
very numerous, even in the 
same plant, and perform many 
of its important functions. 
They are in a sense “cataly- 
zers,’ in that they start or 
intensify chemical processes 
without themselves being used 
up (or only in relatively small 
degree). 
The more important plant en- 
zymes and the substances 
acted upon by them are as 
follows: 
Hydrolyzing saccharose to d- 
glucose and d-fructose. 
Hydrolyzing hemicelluloses to 
monosaccharids. 
