Purification and properties of human acid-thermostable ribonucleases, and diagnosis of childhood pancreatic fibrosis.

Acid-thermostable ribonucleases were isolated from human pancreas, duodenal contents, liver, spleen, serum 
and urine, and purified 15-- 1000-fold. The pH optima, ionic requirements, 
and some of the specificity requirements, of these enzymes were investigated. 
The isolated enzymes formed two distinct groups: (a) The ribonucleases of 
the pancreas, duodenal contents and fraction A of serum and urine 
exhibit a pH optimum of 8.5, are inhibited by An2+ and 
Cu2+, and relatively rapidly hydrolyze the synthetic substrate uridine 3'- (alpha-naphthylphosphate); 
(b) the ribonucleases of the liver and spleen, and of fractions 
B of the serum and urine, with a pH optimum of 
7, are less sensitive to An2+ and Cu2+, and exhibit negligible 
activity versus uridine 3'-(alpha-naphthylphosphate). Determination of the serum level of pancreatic-type 
ribonuclease activity, with the use of uridine 3'-(alpha-naphthylphosphate) or RNA as 
substrates, appears to be a valid diagnostic tool for pancreatic fibrosis 
in children. 