Mukherjea M, Chakraborti A S, Misra S
Biochem Med Metab Biol. 1986 Apr;35(2):115-9. doi: 10.1016/0885-4505(86)90065-4.
Activities and some properties of microsomal ATPases have been studied in developing human placenta. The enzyme activities (Na+ + K+ + Mg2+, Mg2+, and Ca2+ dependent) in the placenta increase steadily with gestational age until the 18th to 21st week, and decrease in the second half of pregnancy. Mg2+-dependent and Na+ + K+ + Mg2+-dependent ATPases possess nearly the same Km (apparent) for ATP, while the Ca2+-dependent enzyme shows a different one. Mg2+-dependent ATPase shows higher substrate affinity than Ca2+-dependent ATPase, although the Vmax of the Mg2+-dependent enzyme is lower than that of the latter. However, for each enzyme, the Km remains almost constant and Vmax varies during ontogenic development. Vmax of the enzymes decline at term. The enzymes are heat-labile, unaffected by amino acids, namely, L-phenylalanine, L-leucine, and L-tryptophan, and deoxycholate inhibits the enzyme activities by about 50%.
已对发育中的人胎盘微粒体ATP酶的活性及某些特性进行了研究。胎盘中的酶活性（依赖于Na⁺ + K⁺ + Mg²⁺、Mg²⁺和Ca²⁺）随孕周稳步增加，直至第18至21周，然后在妊娠后半期下降。依赖于Mg²⁺和Na⁺ + K⁺ + Mg²⁺的ATP酶对ATP具有几乎相同的Km（表观），而依赖于Ca²⁺的酶则表现出不同的Km。依赖于Mg²⁺的ATP酶比依赖于Ca²⁺的ATP酶表现出更高的底物亲和力，尽管依赖于Mg²⁺的酶的Vmax低于后者。然而，对于每种酶，Km在个体发育过程中几乎保持恒定，而Vmax则有所变化。这些酶在足月时Vmax下降。这些酶对热不稳定，不受氨基酸（即L - 苯丙氨酸、L - 亮氨酸和L - 色氨酸）影响，脱氧胆酸盐可抑制酶活性约50%。
