Ribonuclease, cell-free translation-inhibitory and superoxide radical scavenging activities of the iron-binding protein lactoferrin from bovine milk

The purpose of this study was to characterize the ribonuclease (RNase) and cell-free translation-inhibitory activities of lactoferrin isolated from bo vine milk. It was found that bovine lactoferrin exhibited ribonucleolytic a ctivity toward yeast transfer RNA in a dose-dependent manner. The pH optimu m for this RNase activity was in the vicinity of 7.5. Lactoferrin exerted R Nase activity on poly C with an;activity of 2.15U/mg. No activity was detec ted toward poly A, poly G, and poly U. The milk protein inhibited cell-free translation in rabbit reticulocyte lysate with an IC50 of 9.6 mu M. The pr otein was devoid of N-glycosidase activity characteristic of ribosome inact ivating proteins which also possess RNase and cell-free translation-inhibit ory activities. It inhibited superoxide radical formation. (C) 2000 Elsevie r Science Ltd. All rights reserved.