Stimulation and partial stabilization of human histidyl-tRNA synthetase by hemoglobin

Abstract

Histidyl-tRNA synthetase, an enzyme against which antibodies are directed in some patients with polymyositis, has been purified 5000-fold from HeLa cells, but was extremely labile to dilution or on storage at −80°C. In order to facilitate study of the biochemical and immunological properties of the enzyme, a stabilizer was sought. Hemoglobin at 2 mg/ml was found to stimulate the enzyme and also partially preserved the activity of the enzyme stored at a low concentration (< 10μg/ml). Hematin, but not the globin protein, could substitute for hemoglobin in stimulating the enzyme.