Serum Enzymes after Therapeutic Radiation

Abstract

The activity of 11 serum enzymes was studied in patients with carcinoma of the cervix uteri undergoing deep x-ray radiotherapy. These were aldolase, alkaline phosphatase, isocitrate, lactate and malate dehydrogenases, glutamate oxalacetate and glutamate pyruvate transaminases, and four nucleases. While there were no recognizable patterns of enzyme response in the group as a whole, some patients showed pronounced increases in activity of one or more of the enzymes during some stage of radiotherapy. Isocitrate dehydrogenase appeared to be the enzyme most subject to change after radiation.

Involvement of a tyrosine residue in the ADP binding site of creatine kinase. A second‐derivative UV‐spectroscopy study

“…An apparent dissociation constant for MgADP was calculated by the second-derivative spectroscopy technique in the presence or absence of creatine. The value obtained (0.085 mM) agrees closely with those previously determined, either kinetically (18) or by using a fluorimetric technique (26,27). The presence of creatine does not change appreciably the protein affinity for MgADP (0.080 mM).…”

“…The tyrosine/tryptophan ratio of 2.5 deduced from the amino acid content (10 tyrosines and 4 tryptophans) of MM-creatine kinase (17) allows us to calculate a ra value of 0.21. In Table 1, rn and c~ values are summarized for either the enzyme alone or incubated in the presence of MgADP and/or creatine in saturating conditions (18). The rn value measured with native creatine kinase corresponds to an ~ value of 0.591, that is to say 6 tyrosines among the 10 present per monomer.…”