Transferrin antioxidant activity

Gutteridge, J.M.C. (1986). Antioxidant properties of the proteins caeruloplasmin, albumin and transferrin. A study of their activity in serum and synovial fluid fiom patients with rheumatoid arthritis. Biochim. Biophys. Acta 869, 119-127. 

The expression of several genes is induced or repressed by hemopexin-mediated heme transport. Most of these are simple responses of the cell to the increased heme (or iron derived from heme) in the cell. For example, HO-1 is induced (15, 88), ferritin levels rise (14, 61, 89), the transferrin receptor is down-regulated (15), and hemopexin mRNA itself is induced (A. Smith, unpublished). However, MT-1 is also induced, apparently to prepare the cell for oxidative stress thus, in addition to sequestering heme in a low-spin, non-oxidatively active form, hemopexin also indirectly exerts antioxidant effects by inducing MT-1 (16, 61, 90). 

There are several modes of protection from the activity of available iron or copper in vivo. (Antioxidant action is discussed in more detail in Chapter 4). Apotransferrin binds iron(III) for transport and delivery to cells. It is its capacity as an iron-binding protein which renders it also able to function as an antioxidant by making iron(III) unavailable for participation in iron-catalysed radical reactions. Only about 30% of the iron-binding sites on the transferrin in human plasma are normally occupied in vivo (transferrin concentration 1.2-2.0mg/ml). The copper-containing protein caeruloplasmin (0.2-0.4 mg/ml) is... 

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