Hechtman P, Richter A, Corman N, Leong Y M
Department of Biology, McGill University, Montreal, Quebec, Canada.
Pediatr Res. 1988 Dec;24(6):709-12. doi: 10.1203/00006450-198812000-00012.
Deficiency of prolidase is frequently associated with skin lesions and mental retardation. Biochemically, the condition is marked by iminodipeptiduria. We have investigated the feasibility of using donor erythrocytes to replace the deficient enzyme. Prolidase occurs in erythrocytes in an inactive form. If erythrocytes are incubated overnight at 37 degrees C in the presence of 1 mM MnCl2, the intracellular Mn++ concentration increases from 0.014 to 2.04 micrograms/ml. As a consequence, the activity of prolidase in hemolysates increases to 159 mumol glycyl-L-proline hydrolyzed/h/ml compared to 5 mumol/h/ml for hemolysates of cells incubated in the absence of Mn++. Hydrolysis of glycyl-L-proline by intact erythrocytes is reduced by the slow rate of iminodipeptide transport into the cell; however, intact cells hydrolyzed this substrate at a rate 10-20 times faster after preincubation with MnCl2. After exogenous MnCl2 is removed from the storage buffer, high levels of erythrocyte prolidase activity persist for at least 13 days. The kinetic parameters for intact activated erythrocyte-catalyzed hydrolysis of glycyl-L-proline have been estimated. These values predict that donor erythrocytes, activated with Mn++ before transfusion could play a significant role in the recovery of proline from dietary sources of iminodipeptides in patients with prolidase deficiency.
脯氨酰二肽酶缺乏症常与皮肤病变和智力发育迟缓相关。从生化角度来看，该病症的特征是亚氨基二肽尿症。我们研究了使用供体红细胞替代缺陷酶的可行性。脯氨酰二肽酶以无活性形式存在于红细胞中。如果红细胞在1 mM MnCl2存在的情况下于37摄氏度孵育过夜，细胞内Mn++浓度会从0.014微克/毫升增加到2.04微克/毫升。结果，溶血产物中脯氨酰二肽酶的活性增加到159微摩尔甘氨酰-L-脯氨酸水解/小时/毫升，而在无Mn++的情况下孵育的细胞溶血产物的活性为5微摩尔/小时/毫升。完整红细胞对甘氨酰-L-脯氨酸的水解因亚氨基二肽进入细胞的速度缓慢而降低；然而，完整细胞在与MnCl2预孵育后水解该底物的速度快10至20倍。从储存缓冲液中去除外源MnCl2后，高水平的红细胞脯氨酰二肽酶活性至少持续13天。已经估算了完整活化红细胞催化甘氨酰-L-脯氨酸水解的动力学参数。这些值预测，在输血前用Mn++活化的供体红细胞在脯氨酰二肽酶缺乏症患者从饮食来源的亚氨基二肽中回收脯氨酸的过程中可能发挥重要作用。
