Abstract
Summary
Human skeletal muscle extracts at acid pH brought about a loss of myoglobin's antigenic precipitating activity. This property was also present in cardiac muscle, uterine smooth muscle, spleen, liver, and urine, but was absent in serum. The “myoglobinolytic” activity of human skeletal muscle was soluble, nondialyzable, inactive near neutral pH, most active at pH 3.4, stable at 56° for 0.5 hr, and precipitable by ammonium sulfate. It was not possible to obtain adequate separation of this activity using DEAE-cellulose chromatography. Partially purified preparations of this “myoglobinolytic” activity caused the loss of the precipitating ability of myoglobin with antiserum, as well as the loss of its electrophoretic character, and the appearance of new electrophoretic species. The substrate for this reaction appeared to be a complex molecular form of acid myoglobin. The “myoglobinolytic” activity of tissue extracts is presumed to be due to the presence of one or more acid activated proteolytic enzymes. The substrate specificity is not known. However, active fractions did not seem to attack human serum albumin.
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