in experiments carried out with phenylalanine in which all five hydrogens on the aromatic ring have been replaced with deuterium , and in the presence of tetrahydrobiopterin , we have been unable to detect a kinetic isotope effect with either the native hydroxylase or with the hydroxylase activated by limited proteolysis , or by exposure to lysolecithin .
C0020275
hydrogens
C0011744
deuterium