Buletza G F, Smith M E
Biochem J. 1976 Jun 15;156(3):627-33. doi: 10.1042/bj1560627.
Proteolytic activity of central-nervous-system tissue of the normal rat was examined over the pH range 2-9 with casein, haemoglobin and myelin basic protein as substrates. With casein as a substrate, brain and spinal cord homogenates showed very similar activity profiles with increasing pH, with the main peaks of proteolytic activity at pH 3-4 and 5-6. When haemoglobin was used, one broad main peak of activity from pH 3 to 5 was demonstrated. There was no optimum pH, however, for proteolytic activity with myelin basic protein as a substrate, and considerable hydrolysis were observed from pH 3.5 up to pH8. Proteolytic activity at the various pH values was compared by using homogenates of spinal cords from rats with acute experimental allergic encephalomyelitis and those from rats injected with Freund's adjuvant alone. The profiles of activity were similar with peaks at pH 3.5 and 5.5 with casein as a substrate, but the specific activity was significantly higher at most pH values in the spinal-cord homogenates from rats with experimental allergic encephalomyelitis. Similarly the spinal-cord homogenates from these latter rats contained much more proteolytic activity toward myelin basic protein throughout the pH range than was present in the control spinal cords. Homogenates from lymph nodes of rats with experimental allergic encephalomyelitis and from those of the controls contained two to three times as much proteolytic activity as that of the central-nervous-system tissue and had a different proteolytic activity profile form that of the central-nervous system, with higher activity at the neutral than at acid pH. The results are discussed with regard to the probability that inflammatory cells such as lymphocytes may be the cause of the increased proteolytic activity in the central nervous system of animals with experimental allergic encephalomyelitis, and that enzymes from these cells possess the capability of digesting myelin basic protein.
以酪蛋白、血红蛋白和髓鞘碱性蛋白为底物，在pH值2 - 9范围内检测了正常大鼠中枢神经系统组织的蛋白水解活性。以酪蛋白为底物时，脑和脊髓匀浆随着pH值升高呈现出非常相似的活性曲线，蛋白水解活性的主要峰值出现在pH 3 - 4和5 - 6。使用血红蛋白时，在pH 3至5范围内显示出一个宽泛的主要活性峰。然而，以髓鞘碱性蛋白为底物时，蛋白水解活性没有最佳pH值，在pH 3.5至pH8范围内观察到了相当程度的水解。通过使用患有急性实验性过敏性脑脊髓炎的大鼠和仅注射弗氏佐剂的大鼠的脊髓匀浆，比较了不同pH值下的蛋白水解活性。以酪蛋白为底物时，活性曲线相似，峰值出现在pH 3.5和5.5，但在患有实验性过敏性脑脊髓炎的大鼠脊髓匀浆中，大多数pH值下的比活性显著更高。同样，在整个pH范围内，后一组大鼠的脊髓匀浆对髓鞘碱性蛋白的蛋白水解活性比对照脊髓中的活性高得多。患有实验性过敏性脑脊髓炎的大鼠和对照大鼠的淋巴结匀浆中的蛋白水解活性是中枢神经系统组织的两到三倍，并且具有与中枢神经系统不同的蛋白水解活性曲线，在中性pH下的活性高于酸性pH。讨论了这些结果，涉及淋巴细胞等炎性细胞可能是实验性过敏性脑脊髓炎动物中枢神经系统中蛋白水解活性增加的原因，以及这些细胞中的酶具有消化髓鞘碱性蛋白能力的可能性。
