Abstract
Using I131-labeled casein as substrate, the presence of proteolytic activity in human saliva was demonstrated, by measuring the increase of the radioactivity in the non-protein fraction of the incubation mixture and also by employing the so-called quantitative radio-paperchromatography.
This proteolytic activity of saliva had its optimal pH between 6 and 8. It was fairly stable at pH 7.2 and 37°C, but was completely inactivated by heating the saliva in boiling water for 30 mins.
Besides the proteolytic activity, human saliva was found to possess the activity to prevent the precipitation of relatively small amounts of easily precipitable protein by TCA (“anti-TCA activity”), for which salivary mucoid or its related substanc was presumed to be responsible.
Considerably large variations in proteolytic and anti-TCA activities of saliva were observed from person to person as well as from day to day.
