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 bovine milk. It was found that bovine lactoferrin exhibited ribonucleolytic activity toward yeast transfer RNA in a dose-dependent manner. The pH optimum for this RNase activity was in the vicinity of 7.5. Lactoferrin exerted RNase activity on poly C with an activity of 2.15 U/mg. No activity was detected 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 microM. The protein was devoid of N-glycosidase activity characteristic of ribosome inactivating proteins which also possess RNase and cell-free translation-inhibitory activities. It inhibited superoxide radical formation.