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Sephadex G-200 gel filtration of DNA cellulose-treated crude extracts of rat skeletal muscle, revealed a broad peak-fraction of tRNA-inhibitory protein kinases (PK) coeluted endogenous substrates. In comparison, the elution profile of baker's yeast exhibited multiple peak-fractions of tRNA-inhibiting PK. Various tRNA all showed inhibition to PK. In the presence of regulatory subunit of cyclic AMP-dependent protein kinase, tRNA did not exert synergetic inhibition on PK. Moreover, the interaction of tRNA with active muscle PK fractions could not be monitored by the increment of absorbance at 340 nm. tRNA had no significant regulatory effect on the phosphorylation of actin and myosin.

Binding (or interaction) of cortisol with microbial molecule(s) was observed by employing Bio-Gel HTP affinity chromatography and subsequently by fluorescence spectrophotometry. Molecule(s) in the crude extract of baker's yeast and in other microbial proteases exhibited varied degrees of cortisol-binding. Bacterial protease (type IX) had highest, while the type XXVI enzyme had the lowest, binding capacity. In addition, these two proteases exhibited a distinct difference in the alterations of ultraviolet spectra due to interaction with cortisol. Using casein as a substrate, cortisol, CTP, trypsin inhibitor or leupeptin appreciably inhibited type IX protease at low concentrations of Ca2+. However, thyroxine had no effect on this protease.