Weinstein J D, Branchaud R, Beale S I, Bement W J, Sinclair P R
Arch Biochem Biophys. 1986 Feb 15;245(1):44-50. doi: 10.1016/0003-9861(86)90188-8.
Chick embryo liver cells, when cultured for 41 h in the presence of [2-14C]mevalonic acid, took up label and incorporated radioactivity into heme a, but not into protoheme. Incubation of cells with delta-[4-14C]aminolevulinic acid (ALA) resulted in uptake of label and incorporation of radioactivity into both protoheme and heme a. These results show that both protoheme and heme a are synthesized during the incubation period, and that mevalonic acid is a specific precursor of the farnesyl moiety of heme a. Incubation of cells with [1,2-14C]acetate plus N-methyl mesoporphyrin IX, an inhibitor of heme synthesis, resulted in negligible incorporation of label into protoheme and heme a, although cellular lipids were highly labeled. This result indicates that the heme purification methods employed were capable of separating hemes from lipids, and that the measured incorporation of label into hemes from [14C]mevalonic acid and [14C]ALA was not due to lipid contamination.
鸡胚肝细胞在含有[2-¹⁴C]甲羟戊酸的条件下培养41小时后，摄取了放射性标记并将其掺入血红素a中，但未掺入原卟啉。用δ-[4-¹⁴C]氨基乙酰丙酸（ALA）孵育细胞导致摄取放射性标记并将其掺入原卟啉和血红素a中。这些结果表明，在孵育期间原卟啉和血红素a均被合成，并且甲羟戊酸是血红素a的法尼基部分的特定前体。用[1,2-¹⁴C]乙酸盐加血红素合成抑制剂N-甲基中卟啉IX孵育细胞，尽管细胞脂质被高度标记，但原卟啉和血红素a中放射性标记的掺入量可忽略不计。该结果表明所采用的血红素纯化方法能够将血红素与脂质分离，并且从[¹⁴C]甲羟戊酸和[¹⁴C]ALA测得的血红素中放射性标记的掺入并非由于脂质污染。
