Cystic fibrosis: enzymatic detection of a ciliostatic factor.

The ciliostatic cystic fibrosis (CF) factor has been investigated in order to 
develop an enzymatic assay for its detection. In saliva, this factor 
is associated with alpha-amylase. Removal or addition of the factor by 
dialysis does not affect the alpha-amylase catalytic activity of CF or 
control (normal) saliva. Crude preparations of the dialyzable factor from CF 
saliva are ciliostatic. Alpha-Amylase- catalyzed starch hydrolysis from both CF and 
control saliva was found to be insensitive to hydroxyalkylamine inhibitors so 
this method could not be used to detect differences in CF 
and control amylase. Since another carbohydrase, mammalian debranching enzyme, is much 
more sensitive to inhibition, the effect of the isolated crude factor 
on this enzyme was determined. The mean values for percentage of 
inhibition of debranching enzyme activity by fractions obtained from saliva of 
CF patients, obligate heterozygotes, and control subjects are: 32% (27 samples), 
13% (21 samples), and 6% (11 samples), respectively. Fifteen of the 
CF values exceed the maximum 13% inhibition observed for controls. Indeed, 
five samples almost completely inhibited debranching enzyme. This inhibitory action provides 
the basis of an enzymatic assay for the detection of the 
ciliostatic CF factor. 