31
small animals had a higher enzyme activity than those of larger
species.
When considered in terms of the requirements for C05
transport,
the enzyme is present in excess, even among small
animals with high metabolic rates.
It was suggested that car-
bonic anhydrase could influence the oxygen dissociation of
oxyhaemoglobin due to a combination of the following factors:
(1) small animals with high metabolic rates have the largest
CO2 production and the largest amounts of red cell carbonic
anhydrase;
(2)
haemoglobins
gmall animals also have the most acid sensitive
(marked Bohr effect).
Therefore, the enzymatically
accelerated hydration of C032 to carbonic acid might allow the
Bohr effect,
in small animals,
to cause delivery of more oxygen
to the tissues during the short time the red cells remain in
the capillaries,
In recent years,
the carcinogenic properties of heavy
metals have come under increasing scrutiny by cancer researchers.
Halme
(1961) demonstrated the carcinogenic properties of zinc
in experiments with various levels of zinc in the drinking water
of mice.
The relation between the properties of heavy metals
and enzyme activity in carcinogenesis has been discussed by
Furst (1960), who hypothesized that (1) some metals can cause
cancer,
and (2) once within a cell,
these metals may modify the