Formaldehyde Inhibition of Tryptic and Peptic Digestion of Egg White. ∗

In connection with a study of the action of formaldehyde on certain bacterial suspensions, 1 parallel observations were made of its effect on trypsin and pepsin. Little work has been reported on the influence of formaldehyde on tryptic and peptic digestion of proteins. Johannessohn 2 found that preparations of trypsin vary in their susceptibility to this aldehyde; activity of one preparation was unaffected by 20 hours standing with 1% formaldehyde, while that of another was inhibited by 1/20% formaldehyde. He also reported that pepsin was not inactivated by 10% formaldehyde in 24 hours.

In our experiments, however, formaldehyde in low concentrations had a marked inhibitory effect on the action of both trypsin and pepsin on egg-white. Complete inactivation was not accomplished, however, by the presence of 4% formaldehyde as shown by 18 hour digestion. (Table I.)

Two solutions of raw egg white containing 0.25% and 2.5% protein respectively and 0.4% trypsin∗ were divided into 10 cc. volumes, and each series treated with varying concentrations of formaldehyde. The reaction was adjusted to pH 7.4 and the mixtures allowed to digest at 37-40° for 18 hours. Similar concentrations of macerated coagulated egg white were digested with 0.1% pepsin at pH 2.5. At the end of the digestion period the liquids were neutralized and the extent of digestion determined by means of Sorensen's formol titration method.

The results in the case of the series containing 2.5% egg white are given in the accompanying table.