805 
7th Series of experiments. Enzyme R diluted with 1 vol. of water. 
= | nn 
H,0 | Amy-, En- qh Reaction (determined at 18°) 
Regulating mixture lum (zyme 4G, p 
/ Oh Gs Ale C.C Ei H 
| | de 
a none 50 200 2 318.20  electrometrical determination 
not practicable on account of 
the lack of electrolytes. Neutral 
| _ behaviour to litmus, so 
| PH +707 
b 10c.c.phosphoricacid 19.4 200 2 245.05 1.07 
20.6 c.c. NaOH 
c 10c.c.phosphoricacid 23.75 200 2 | 425.15 6.50 
16.25 c.c. NaOH 
d 10 c.c. citrate, 20.45 200 2 221455: | 6.468 
19.55 c.c. NaOH 
a comparison between citrate and phosphate shows that inhibition 
is much stronger with the former than with the latter. 
From the removal of the optimal reaction towards the neutral 
point, as well as from the tests published in this paper, it is appa- 
rent, that citrate inhibits most strongly on the side of the minor 
pu’s, and that this impeding action weakens towards the neutral 
point. ; 
The optimal reactions being identical in phosphate- and acetate- 
mixtures, it was likely, that either of them should slacken the action 
of the ptyalin in the same way. The following test illustrates the 
fact that, if the reactions are the same, both mixtures equally affect 
the enzymic action. 
&th Series of experiments. Enzyme R diluted with one vol. water. 
H20 Amylum Enzyme Reduction 
| Regulator Cr. Ba) Thi ee mGr. Cu H 
a 10 cc. of acetate 35 200 2 489.2 5.886 
5 c.c. of acetic acid | | 
b 10c.c.of phosphoric | 26 200 2 483.5 | 5.886 
| acid 14 c.c. NaOH 
We now passed on to inquire how this influence of the reaction 
upon the action of ptyalin is to be accounted for. It may indeed be 
imagined, that H-ions favour the enzymic action, but how is it then 
that beyond the optimal cy they largely impede the activity. Is it 
perhaps to be attributed to an injury to the enzyme? In order to 
find this out we made the following experiments: 
| 53 
Proceedings Royal Acad. Amsterdam, Vol. XV. 
