8. They may be adsorbed like other colloids by “shaking out” with finely divided suspensions like charcoal or kaolin, or by other colloids like aluminum hydroxide or proteins.
9. When properly introduced into the tissues or blood of an animal, they cause the body cells to form anti-enzymes which will prevent the action of the enzyme (see [Chapter XXVII]).
10. Though inert, they show many of the characteristics of living organisms, that is
(a) Each enzyme has an optimum, a maximum and a minimum temperature for its action.
All chemical reactions have such temperature limits, the distinction is that for enzymes as for living substance the range is relatively narrow.
(b) High temperatures destroy enzymes. All in water are destroyed by boiling in time and most at temperatures considerably below the boiling-point. When dry, many will withstand a higher degree of heat than 100° before they are destroyed.
(c) Temperatures below the minimum stop their action, though they are not destroyed by cold.
(d) Many poisons and chemical disinfectants ([Chapter XIV]) which kill living organisms will also stop the action of enzymes, though generally more of the substance is required, so that it is possible to destroy the living cells by such means and yet the action of the enzyme will continue.
(e) Most enzymes have an optimum reaction of medium either acid, alkaline or neutral, depending on the particular enzyme, though some few seem to act equally well within a considerable range on either side of the neutral point.
The final test for an enzyme is the chemical change it brings about in the specific substance acted on.