Concentrations of trypsin, elastase and carbohydrate antigen CA 19-9 in serum of cystic fibrosis patients.

CLINICALCHEMISTRY, Vol. 32, No. 5, 1986 913 with either substrate, but the observed activity was 55.7% lower with iralanine-4-nitroanilide, in contrast with what happens in sera of males and nonpregnant women. Evidently, i..-alanine-4-mtroanilide behaves like LCHA in this regard, probably reflecting the relative resistance of these substrates to the action of cystyl-aminopeptidase and perhaps other a-aminoacylpeptide hydrolases whose activity may be increased in the sera during pregnancy. We thus find this method to be fast, kinetic, and readily amenable to total automation, and we believe it has practical and theoretical advantages over those in which LCHA is used as substrate.