IMMUNOENZYMOLOGY-REACTION PROCESSES, KINETICS AND THE ROLE OF CONFORMATIONAL ALTERATION*

Serological evidence for the alteration of enolase during aging

Pure enolase isolated from young and old Turbatrix aceti has been compared using immunologic techniques. Antiserum prepared to "young" and "old" enolase, respectively, will completely precipitate either enzyme. However, antiserum prepared to "young" enolase reacts more efficiency with "young" than with "old" than with "old" enzyme and vice versa. A third form of enolase (inactive enolase) is found in homogenates of old organisms. This material yields a pattern of identity with "young" enolase and partial identity with "old" enolase. It also gives rise to specific antibodies which do not react with "young" or "old" enolase. The material appears to accumulate with age. The results indicate a close structural relationship between "young", "old" and inactive enolase.

Inhibition of lobster-muscle arginine kinase by homologous antibodies and study of an antibody population directed against a tyrosine-containing antigenic structure

The effect of highly inhibitory rabbit antibodies on the enzymic activity of lobster-muscle arginine kinase has been studied. 100% inhibition was obtained at a 30-fold molar excess of antibody. The guanidine substrate L-arginine did not protect the enzyme from subsequent inhibition by its antibodies. On the other hand, the metal-nucleotide substrate Mg-ATP, or the substrate analog Mg-AMP, protected about 50% the enzyme activity, the extent of hte protection being irrespective of hte presence or of the absence of L-arginine and of the value of the molar ration Ab/Ag/ An antibody population directed against the antigenic determinant containing the essential tyrosine residue of the enzyme has been isolated by the affinity chromatography. No inhibitory acitivity was found in that fraction. Most of the inhibitory activity was found in the remaining antibody populations...

Quantitation of creatine kinase isoenzymes in human tissues and sera by an immunological method

Antisera against the crystallized creatine kinase isoenzymes from human skeletal muscle (MM) and from human brain (BB) were produced in rabbits. Both the MM and BB isoenzymes were precipitated quantitatively by their homologous antisera. No cross-reaction was observed. Thy hybrid MB from human heart muscle could not be precipitated completely by either of the two antisera. In artificial mixtures the concentrations of individual creatine kinase isoenzymes were determined from the percentage of non-precipitable activity in the supernatant after reaction with each of the antisera. This immunotitration assay was applied to study the quantitative distribution of creatine kinase compared with those determined by electrophoretic analysis. In sera of patients with myocardial infarction, the immunotitration assay allowed the sensitive and rapid quantitation of creatine kinase isoenzymes, especially of the "infarct-specific" hybrid MB, even in sera with low total activity. This indicates that the method is of diagnostic value.

Immunochemical studies on glutamate dehydrogenase and on two mutant forms of the protein

Studies on the active product of pepsin digestion of rabbit immunoglobulin G (IgG), F(ab')(2) produced from antiserum against Neurospora glutamate dehydrogenase, showed it to behave in the same way, in both antienzyme and precipitation experiments, as homologous IgG. It is proposed that the inhibition of glutamate dehydrogenase by this antibody preparation is by the same mechanism as proposed for IgG and F(ab), a change in the configuration of the catalytic site brought about by antibodies. Antibodies prepared against two mutant proteins behaved in antienzyme studies in the same way as antibodies prepared against the wild-type protein. It is thought therefore that the antigenic sites on the mutant proteins which initiate the production of neutralizing antibodies were not affected by the mutation which had changed the catalytic properties of the mutant proteins.