Lysyl hydroxylase 3 is a multifunctional protein possessing collagen glucosyltransferase activity

Lysyl hydroxylase (EC 1.14.11.4) and glucosyltransferase (EC 2.4.1.66) are enzymes involved in post-translational modifications during collagen biosyn thesis, We reveal in this paper that the protein produced by the cDNA for h uman lysyl hydroxylase isoform 3 (LH3) has both lysyl hydroxylase and gluco syltransferase (GGT) activities. The other known lysyl hydroxylase isoforms , LH1, LH2a, and LH2b, have no GGT activity, Furthermore,: antibodies recog nizing the amino acid sequence of human LH3 and those against a highly puri fied chicken GGT partially inhibited the GGT activity. Similarly, a partial inhibition was observed when these antibodies were tested against GGT extr acted from human skin fibroblasts. In vitro mutagenesis experiments demonst rate that the amino acids involved in the GGT active site differ from those required for LH3 activity.