February 15, 1951
Dear Arthur:
I read your abstract in Fed. Proc. 1950 again, after Gerty told me about your interest in the adenylic effect on the DPN specific "isocitric dehydrogenase" in yeast.  You have undoubtedly considered this, but for my own information, could isocitric be decarboxylated first, leaving A-hydroxyglutaric acid, followed by dehydrogenation over DPN.  In other words, have you tried A-hydroxyglutaric acid + DPN <=> A-ketoglutaric acid + DPNM to the right (or to the left, if equilibrium not too unfavorable).
Best regards,
Sincerely,
Carl F. Cori
P.S. Adenylic could act by "laying on of hands;" at least, that is what we say about its action on phosphorylase.  What mysterious creatures enzymes are.