Infants who consume casein hydrolysate formula have been shown to have lowe
r neonatal jaundice levels than infants who consume. routine formula or bre
ast milk. Because casein hydrolysate has been shown to contain a beta -glac
uronidase inhibitor, one possible mechanism to explain this finding is bloc
kage of the enterohepatic circulation of bilirubin by a component of the fo
rmula. The aim of this research was to identify the source of the beta -glu
curonidase inhibition in hydrolyzed casein. A beta -glucuronidase inhibitio
n assay and measurements of physical and kinetic parameters were used to an
alyze the. components of hydrolyzed casein and infant formulas. Kinetic stu
dies used purified beta -glucuronidase. The L-aspartic acid in. hydrolyzed
casein accounts for the majority of the beta -glucuronidase inhibition pres
ent. Kinetic studies indicate a competitive inhibition mechanism. L-Asparti
c acid is a newly identified competitive inhibitor of beta -glucuronidase.