Key points are not available for this paper at this time.
The reaction catalyzed by galactosyltransferase has been studied kinetically at pH 8.0 using glucose as the galactosyl group acceptor in the presence of a fixed concentration of α-lactalbumin. The initial velocity patterns and the patterns for the dead-end inhibition by UDP-glucose were similar to those obtained with N-acetylglucosamine as a substrate in the absence of α-lactalbumin (in an accompanying paper). l -Arabinose acted as a dead-end inhibitor giving rise to inhibitions which were competitive with respect to glucose and uncompetitive in relation to both Mn2+ and UDP-galactose. These results have been interpreted to indicate that there is an ordered addition of Mn2+, UDP-galactose, and glucose to the enzyme, as well as an ordered release of lactose and UDP. It is postulated that Mn2+ does not dissociate from the enzyme-manganese complex during the catalytic reaction. Product inhibition by lactose was not observed. Comparisons have been made of the values for the kinetic constants associated with Mn2+ and UDP-galactose in the absence and presence of α-lactalbumin.
Morrison et al. (1971) studied this question.