Studies on human placental glutathione S-transferase. Multiplicity and mother age influence.

Human placental glutathione S-transferase was purified to apparent homogeneity by direct application of the crude homogenate into glutathione linked sepharose affinity chromatography. Chromatofocusing analysis in the presence of reduced glutathione resolved the enzyme into three acidic peaks eluted at pH 6.0, 5.7 and 5.5. About 36% of the initial activity was recovered in the isozyme fraction eluted at pH 6.0 whereas the isozymes eluted at pH 5.7 and 5.5 accounted for 20% and 25% of the activity respectively. Disc gel electrophoresis in the presence of sodium dodecyl sulfate revealed the presence of a single protein band in all the three separated isozymes. These isozymes were homodimers with an apparent relative molecular mass of 44.000 and subunit molecular mass of 21.000. The isozymes were immunologically related to each other and to the enzyme from goat and sheep placentae. Mother age had no influence in the placental glutathione S-transferase activity, albeit the activity was slightly higher in placenta obtained from younger women.