27
Cartilage and joint fluids, the mechanical properties of mucosubstances may be regulated by the nature of metallic cations
in the body fluids.
3.22
Zinc.
As in the case of other metals occurring in
only minor amounts in biological systems, the abundance of
zine with relation to the major components is in no way related
to its importance in sustaining the life processes of these
systems.
The biological significance of zinc has been reviewed
by Vallee
(1957) who studied its physiological role in its
relationship to proteins,
specifically those having enzymic
activity.
Until recently, the only physiological role accepted for
zinc was related to its presence as an active component of the
enzyme carbonic anhydrase,
Keilin and Mann (1940).
in which it was first noted by
This enzyme catalyzes the reaction
CO2 + H,0= H2CO3, increasing the rate of COz exchange to a
level sufficient to sustain life.
Zinc is an integral part of
the molecule of carbonic anhydrase which is irreversibly inactivated by the removal of zinc.
bine with zinc
sulfonamides)
(dimercaprol,
Enzyme inhibitors that com-
cyanide,
sulfide,
azide and
effect a reversible inactivation of the enzyme,
Its ubiquitous distribution in tissues suggested that carbonic
anhydrase might account for all of the zinc in tissues.
Except