III. THE RIBONUCLEASES OF HUMAN EPIDERMIS

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Abstract
Sodium acetate and sulfuric acid extracts of human epidermis could each be separated by chromatographic techniques into 3 or more fractions with RNase activity. Eight of these fractions were compared with respect to MW, pH activity profile, polyribonucleotide hydrolysis and activity in the presence of low levels of spermidine. Sodium acetate and sulfuric acid extracts were also prepared from callus and from psoriatic lesions and compared with extracts from normal epidermis for their response to exogenous spermidine. All 8 human epidermal RNase fractions studied had an apparent MW of 15,000 daltons. Seven of the RNase fractions were optimally active at alkaline pH (pH 7.3-7.6 in sodium phosphate and pH 8.1 in Tris-HCl) while the 8th RNase was most active at pH 5.6 in a citrate-phosphate buffer. All enzymes hydrolyzed polycytidylic acid and 5 also hydrolyzed polyuridylic acid. None hydrolyzed polyadenylic acid. Seven of the 8 RNase studied exhibited greater activity in the presence of added spermidine. The extracts from psoriatic scales showed markedly elevated RNase levels which could not be raised further by the addition of spermidine.

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