Williams-Smith D L, Morrison P J
Biochim Biophys Acta. 1975 Oct 20;405(2):253-61. doi: 10.1016/0005-2795(75)90092-6.
The relatively small number of paramagnetic species and the high concentration of catalase in mammalian liver and blood make it possible to directly study this enzyme in frozen whole tissue. The EPR spectra of catalase are dependent on the heme environment and in human blood only catalase A, gxy = 6.48, 5.36 is observed whereas in liver a second spectrum, catalase B, gxy = 6.80, 5.07 can also be seen. Using rapid freeze techniques it has been shown that in rat liver catalase A corresponds to the in vivo steady state and that after death this is largely converted into catalase B. Data from the perfusion of rat livers with oxygenated and deoxygenated blood and dextran solutions together with results from in vitro studies of catalase are interpreted as indicating that catalase B results from the interaction of catalase with an organic acid, most probably formic acid, that the acid is a peroxidative substrate for catalase in vivo and that peroxidation of the acid is not the major role for catalase in rat liver. Catalase binding with other small molecules in intact liver has been demonstrated by perfusion with nitrite-containing dextrans and by intraperitoneal injection of 3-amino-1,2,4-triazole.
哺乳动物肝脏和血液中顺磁性物质数量相对较少以及过氧化氢酶浓度较高，使得在冷冻的全组织中直接研究这种酶成为可能。过氧化氢酶的电子顺磁共振光谱取决于血红素环境，在人血液中仅观察到过氧化氢酶A，gxy = 6.48, 5.36，而在肝脏中还可以看到第二种光谱，即过氧化氢酶B，gxy = 6.80, 5.07。使用快速冷冻技术已表明，在大鼠肝脏中过氧化氢酶A对应于体内稳态，并且在死亡后，这在很大程度上转化为过氧化氢酶B。用含氧和脱氧血液以及右旋糖酐溶液灌注大鼠肝脏的数据，连同过氧化氢酶的体外研究结果，被解释为表明过氧化氢酶B是过氧化氢酶与一种有机酸（很可能是甲酸）相互作用的结果，该酸是体内过氧化氢酶的一种过氧化底物，并且该酸的过氧化不是大鼠肝脏中过氧化氢酶的主要作用。通过用含亚硝酸盐的右旋糖酐灌注以及腹腔注射3-氨基-1,2,4-三唑，已证明完整肝脏中过氧化氢酶与其他小分子的结合。
