280
JOHN RUNNSTRÖM
F. Enzyme Activation by Removal of Inhibitors
Runnström (1949) contended that the effective attachment of the
spermatozoon brings about the release of a "kinase" from an inhibitor.
The "kinase" would then bring some other key enzymes into an active
state. The tentative view was submitted that the inhibitors might be
identical with a heparin-like substance (loc. cit. p. 314). This concept
may today be regarded as an oversimplification, particularly in view of
the considerations presented in Sections ΙΙ,Α and C. If there are several
steps in the activation of the egg there may also be several inhibitors
that can be removed upon fertilization. One possibility is that the same
inhibitor could act on several different enzyme systems or that at least
the inhibitors could be related substances. In this respect mucopolysaccharides offer great possibilities. They are active as inhibitors of a number of peptidases, phosphatases, and of ribonuclease (see Gibian, 1959).
Two ways were tried in the past for testing the view presented by Runnström. The first was the application of acid mucopolysaccharides to the
egg surface in order to increase the effect of the "natural inhibitor"
(Runnström and Hagström, 1955). The other method was the treatment
of eggs with concentrations of sodium periodate which cause a rapid
decrease of the viscosity of dissolved jelly coat substance (Runnström
and Kriszat, 1950b). The first line of investigation was started by testing the effect of heparin and of dissolved jelly coat substance. An inhibition of fertilization, or at least an impairment and delay of the cortical reactions, was found as an effect of exposure to these substances
before and during insemination (Runnström and Wicklund, 1950).
Harding (1951) continued this work and used a commercial preparation
of heparin which had a particularly strong inhibitory effect. This effect
was completely removed by addition of 5 Χ 10~
5 M NaI0 4 to an egg
suspension exposed to heparin (Runnström and Kriszat, 1950b; Harding, loc. cit). According to Harding, heparin is active also after the removal of the jelly coat from the egg; moreover, it proved active on eggs
in which the vitelline membrane was broken up or removed by trypsin
treatment. It seems, thus, that heparin acts directly on the cytoplasmic
surface of the egg, probably by entering in combination with the protein
layer present there, which is conjugated with the lipids of the plasma
membrane, on one hand, and in intact eggs with the vitelline membrane,
on the other.
An inhibitory effect similar to that of heparin was exerted by other
sulfated mucopolysaccharides such as human H substance and chondroitin sulfate. Extensive work was carried out with the last substance
and with the less active dextran sulfate by Β. E. Hagström, U. Esping,
JOHN RUNNSTRÖM
F. Enzyme Activation by Removal of Inhibitors
Runnström (1949) contended that the effective attachment of the
spermatozoon brings about the release of a "kinase" from an inhibitor.
The "kinase" would then bring some other key enzymes into an active
state. The tentative view was submitted that the inhibitors might be
identical with a heparin-like substance (loc. cit. p. 314). This concept
may today be regarded as an oversimplification, particularly in view of
the considerations presented in Sections ΙΙ,Α and C. If there are several
steps in the activation of the egg there may also be several inhibitors
that can be removed upon fertilization. One possibility is that the same
inhibitor could act on several different enzyme systems or that at least
the inhibitors could be related substances. In this respect mucopolysaccharides offer great possibilities. They are active as inhibitors of a number of peptidases, phosphatases, and of ribonuclease (see Gibian, 1959).
Two ways were tried in the past for testing the view presented by Runnström. The first was the application of acid mucopolysaccharides to the
egg surface in order to increase the effect of the "natural inhibitor"
(Runnström and Hagström, 1955). The other method was the treatment
of eggs with concentrations of sodium periodate which cause a rapid
decrease of the viscosity of dissolved jelly coat substance (Runnström
and Kriszat, 1950b). The first line of investigation was started by testing the effect of heparin and of dissolved jelly coat substance. An inhibition of fertilization, or at least an impairment and delay of the cortical reactions, was found as an effect of exposure to these substances
before and during insemination (Runnström and Wicklund, 1950).
Harding (1951) continued this work and used a commercial preparation
of heparin which had a particularly strong inhibitory effect. This effect
was completely removed by addition of 5 Χ 10~
5 M NaI0 4 to an egg
suspension exposed to heparin (Runnström and Kriszat, 1950b; Harding, loc. cit). According to Harding, heparin is active also after the removal of the jelly coat from the egg; moreover, it proved active on eggs
in which the vitelline membrane was broken up or removed by trypsin
treatment. It seems, thus, that heparin acts directly on the cytoplasmic
surface of the egg, probably by entering in combination with the protein
layer present there, which is conjugated with the lipids of the plasma
membrane, on one hand, and in intact eggs with the vitelline membrane,
on the other.
An inhibitory effect similar to that of heparin was exerted by other
sulfated mucopolysaccharides such as human H substance and chondroitin sulfate. Extensive work was carried out with the last substance
and with the less active dextran sulfate by Β. E. Hagström, U. Esping,