Megumi Otsuka

Effects of L -Ascorbic Acid on Lysyl Oxidase in the Formation of Collagen Cross-links

To clarify the role of L-ascorbic acid (AsA) in the formation of pyridinoline, we examined the effects of AsA in vitro using soluble collagen and partially purified lysyl oxidase from bovine aorta. The concentration of dehydrodihydroxylysinonorleucine decreased when AsA was added in the early stage of pyridinoline formation. However, when AsA was added in a later stage of pyridinoline formation, the concentration of pyridinoline was not affected. These findings indicated that AsA was involved in the initial enzymatic reaction in pyridinoline synthesis. We purified lysyl oxidase to confirm its association of AsA. AsA inhibited the enzyme activity. Erythorbic acid and 3,4-dihydroxybenzoate suppressed the enzyme activity as well as AsA did. The inhibition by AsA of the lysyl oxidase activity arose from characteristics of AsA structure. AsA might be important in the regulation of the oxidative reaction of lysine.

Role of Supplemental Ascorbate on Regulation of Growth in Cultured Cells

L-Ascorbic acid is widely consumed as a dietary supplement with the goal of prophylaxis or treatment for health aberrations. Possible mechanisms of ascorbate (AsA) that alleviate the physiological changes caused by certain life hazards and diseases have been elucidated. AsA is known to act as an anitioxidant and a prooxidant in vitro, but it is thought that the adverse effects induced by high amounts of AsA are unlikely to be important in vivo. In general, the AsA content in tissues decreases with age, and high intake of AsA appears promising for protection against oxidative stress during aging. Here, we review our findings concerning to the effects of AsA on cell growth.