Vitamin-C Transport
Vitamin-C (Ascorbate or Ascorbic Acid) is an essential water-soluble Vitamin, well known for its antiscorbutic and antioxidant functions in humans. Vitamin-C was first identified by virtue of the essential role it plays in Collagen modification, preventing the nutritional deficiency Scurvy. Vitamin-C acts as a cofactor for the P4H (Prolyl Hydroxylase) enzymes, which post-translationally modify Collagen and thereby increase the strength and elasticity of tissues. Vitamin-C reduces the metal ion prosthetic groups of many enzymes, thereby maintaining the activity of enzymes. The fact that prevention of Scurvy through modification of Collagen is the most obvious role for Vitamin-C; it is not necessarily the only role of Vitamin-C (Ref.1). Collagen modification depends on the Vitamin-C concentration within the tissues and requires regular dietary intake and active transport of the Vitamin within tissues. Vitamin-C/Ascorbate absorbed from nutrients enters the intestinal epithelium and are accumulated in the blood plasma through Ascorbate transporters. SVCTs (Sodium-Dependent Vitamin-C Transporters) are Ascorbate transporters for Vitamin-C import into cells. These transporters specifically transport reduced L-Ascorbic Acid against a concentration gradient using the intracellular Sodium gradient to drive Ascorbate transport. SVCTs are expressed in the cells of spleen, brain, eye, pancreas, testis, ovary, adrenal gland, lung etc (Ref.2 & 3).