9. COMPARATIVE BIOCHEMISTRY OF GLYCOLYSIS
429
reduced the activity of this enzyme; its inhibitory potency on lactic dehydrogenase of rat muscle was significantly lower while it had no effect
on the lactic dehydrogenase of schistosomes (254). Conversely, following immunization of roosters against lactic dehydrogenase of Schistosoma
mansoni, the serums of these animals decreased the activity of schistosome lactic dehydrogenase, but not that of lactic dehydrogenase of rabbit
muscle (255).
Incubation of phosphoglucose isomerase of schistosomes with an
antiserum against this enzyme produced a sharp decline in the activity
of the schistosome isomerase, but did not interfere with the catalytic
function of this enzyme in the same reaction in rabbit muscle (180).
The antiserum against the schistosome isomerase did not affect the activity of lactic dehydrogenase of the same parasite and, conversely, the
immune serum against the latter enzyme had no effect on the isomerase
of schistosomes (256). Because of the absence of cross-reactions, it is
evident that these antiserums react with sites specific for a particular
enzyme, rather than with groupings common to schistosome proteins.
The specificity of enzyme-antibody reactions is illustrated also by the
observations that the antiserum against yeast glyceraldehyde-3-phosphate
dehydrogenase had no effect on yeast hexokinase (252), and that the
antiserum against rabbit muscle lactic dehydrogenase did not affect the
activities of phosphoglucose isomerase, of aldolase, and of glyceraldehyde-3-phosphate dehydrogenase of rabbit muscle (254), indicating
again that these antibodies react with sites specific for a particular enzyme of a given species. While the species specificity of enzymes has
been tested only in a limited number of instances, it should be pointed
out that there has been no case where homologous enzymes from different species were found to be identical. A recent investigation of Henion
and Sutherland (256) has revealed that an enzyme may be specific not
only for a particular species, but also for a single tissue or organ of the
same species; an antiserum to dog heart phosphorylase inhibited this
enzyme but had no effect on dog liver phosphorylase. Preincubation of
the enzyme with the substrate or coenzyme afforded protection from the
inhibitory effects of some of the antiserums (180, 255). It appears that,
in these instances, at least one point of attachment of the antibody is
localized either at the active center of the enzyme or in such close
proximity to the active center that combination of the substrate or coenzyme with the enzyme prevented interaction with the antibody.
Unless the active center is involved in a more direct manner, the
protective effects of coenzymes do not prove necessarily that the active
centers, rather than some other constituents of homologous enzymes,
differ from each other, particularly if the functional characteristics of
429
reduced the activity of this enzyme; its inhibitory potency on lactic dehydrogenase of rat muscle was significantly lower while it had no effect
on the lactic dehydrogenase of schistosomes (254). Conversely, following immunization of roosters against lactic dehydrogenase of Schistosoma
mansoni, the serums of these animals decreased the activity of schistosome lactic dehydrogenase, but not that of lactic dehydrogenase of rabbit
muscle (255).
Incubation of phosphoglucose isomerase of schistosomes with an
antiserum against this enzyme produced a sharp decline in the activity
of the schistosome isomerase, but did not interfere with the catalytic
function of this enzyme in the same reaction in rabbit muscle (180).
The antiserum against the schistosome isomerase did not affect the activity of lactic dehydrogenase of the same parasite and, conversely, the
immune serum against the latter enzyme had no effect on the isomerase
of schistosomes (256). Because of the absence of cross-reactions, it is
evident that these antiserums react with sites specific for a particular
enzyme, rather than with groupings common to schistosome proteins.
The specificity of enzyme-antibody reactions is illustrated also by the
observations that the antiserum against yeast glyceraldehyde-3-phosphate
dehydrogenase had no effect on yeast hexokinase (252), and that the
antiserum against rabbit muscle lactic dehydrogenase did not affect the
activities of phosphoglucose isomerase, of aldolase, and of glyceraldehyde-3-phosphate dehydrogenase of rabbit muscle (254), indicating
again that these antibodies react with sites specific for a particular enzyme of a given species. While the species specificity of enzymes has
been tested only in a limited number of instances, it should be pointed
out that there has been no case where homologous enzymes from different species were found to be identical. A recent investigation of Henion
and Sutherland (256) has revealed that an enzyme may be specific not
only for a particular species, but also for a single tissue or organ of the
same species; an antiserum to dog heart phosphorylase inhibited this
enzyme but had no effect on dog liver phosphorylase. Preincubation of
the enzyme with the substrate or coenzyme afforded protection from the
inhibitory effects of some of the antiserums (180, 255). It appears that,
in these instances, at least one point of attachment of the antibody is
localized either at the active center of the enzyme or in such close
proximity to the active center that combination of the substrate or coenzyme with the enzyme prevented interaction with the antibody.
Unless the active center is involved in a more direct manner, the
protective effects of coenzymes do not prove necessarily that the active
centers, rather than some other constituents of homologous enzymes,
differ from each other, particularly if the functional characteristics of