性能描述

Biochem/physiol Actions
Vitamin B12 (cobalamin) refers to a group of chemically-related cobalt containing molecules involved in cell processes such as DNA synthesis, fatty acid synthesis, energy production and regulation. The physiologically active forms of vitamin B12 include methylcobalamin and adenosylcobalamin, whereas hydroxocobalamin (vitamin B12a, OHCbl) and cyanocobalamin (CNCbl) are storage and delivery forms. Bacteria-derived hydroxocobalamin (OHCbl) and CNCbl are converted in humans to useful coenzyme forms to support metabolic processes such as mitochondrial methylmalonylcoenzyme A mutase conversion of methylmalonic acid (MMA) to succinate to link lipid and carbohydrate metabolism, and activation of methionine synthase, the rate limiting step in the synthesis of methionine.

维生素B12是一种含有3价钴的多环系化合物，4个还原的吡咯环连在一起变成为1个咕啉大环（与卟啉相似），是维生素B12分子的核心。所以含这种环的化合物都被成为类咕啉。维生素B12为浅红色的针状结晶，易溶于水和乙醇，在pH值4.5～5.0弱酸条件下最稳定，强酸（pH<2）或碱性溶液中分解，遇热可有一定程度破坏，但短时间的高温消毒损失小，遇强光或紫外线易被破坏。