Packman S, Caswell N, Gonzalez-Rios M C, Kadlecek T, Cann H, Rassin D, McKay C
Am J Hum Genet. 1984 Jan;36(1):80-92.
In biotin-responsive multiple carboxylase deficiency, a characteristic organic aciduria reflects in vivo deficiency of mitochondrial propionyl CoA carboxylase, 3-methylcrotonyl CoA carboxylase, and pyruvate carboxylase. A possible primary or secondary defect in biotin absorption leads to an infantile-onset syndrome, while abnormal holocarboxylase synthetase activity has been identified in the neonatal-onset form. While distinct mitochondrial and cytosolic holocarboxylase synthetase biotinylation systems may exist in avian tissues, the system has not been characterized in humans. Toward this objective, we studied the biotin dependence of a cytosolic carboxylase, acetyl CoA carboxylase (ACC), in cultured skin fibroblasts of both types of multiple carboxylase deficiency. ACC specific activities in control and infantile-onset cells were not distinguishable at all biotin concentrations: with decreasing biotin availability (+ avidin), there were only modest decrements in ACC activity in both these cell types. In contrast, there were pronounced declines of ACC activity in neonatal-onset (holocarboxylase synthetase-deficient) cells after growth in low biotin concentrations, and activity was undetectable in + avidin. ACC activity was rapidly restored with biotin repletion to biotin-starved holocarboxylase synthetase-deficient cells, and this restoration was largely independent of protein synthesis. The behavior of the cytosolic carboxylase, ACC, is in all these respects identical to that of the mitochondrial carboxylases, an observation consistent with the existence of similar biotinylation mechanisms in the two cell compartments. Further, the data support the notion that at least some components of the holocarboxylase synthetase system are shared by mitochondria and cytosol in humans, and are consistent with the suggestion that restoration of activity in biotin-depleted cells represents biotinylation of preexisting enzyme protein. The modest decrements in ACC activity in normal and infantile-onset cells may be related to the compromised epidermal integrity observed in that form of multiple carboxylase deficiency. Finally, ACC and mitochondrial carboxylase activities were compared in cells from mutants representing a spectrum of clinical severity. Cells from later-onset patients of intermediate clinical severity were ultimately classifiable as putative holocarboxylase synthetase-deficient cells on chemical criteria. Accurate etiologic classification cannot be based on clinical presentation alone, and biochemical studies should be performed on all patients. Accordingly, we propose a classification of multiple carboxylase deficiency based on biochemical criteria.
在生物素反应性多种羧化酶缺乏症中，一种特征性的有机酸尿症反映了体内线粒体丙酰辅酶A羧化酶、3-甲基巴豆酰辅酶A羧化酶和丙酮酸羧化酶的缺乏。生物素吸收可能存在的原发性或继发性缺陷会导致婴儿期发病的综合征，而在新生儿期发病的形式中已发现全羧化酶合成酶活性异常。虽然禽类组织中可能存在不同的线粒体和胞质全羧化酶合成酶生物素化系统，但该系统在人类中尚未得到表征。为了实现这一目标，我们研究了两种类型多种羧化酶缺乏症的培养皮肤成纤维细胞中胞质羧化酶乙酰辅酶A羧化酶（ACC）对生物素的依赖性。在所有生物素浓度下，对照细胞和婴儿期发病细胞中的ACC比活性没有差异：随着生物素可用性降低（添加抗生物素蛋白），这两种细胞类型中的ACC活性仅适度下降。相比之下，在低生物素浓度下生长后，新生儿期发病（全羧化酶合成酶缺陷）细胞中的ACC活性显著下降，在添加抗生物素蛋白的情况下检测不到活性。向生物素饥饿的全羧化酶合成酶缺陷细胞补充生物素后，ACC活性迅速恢复，并且这种恢复在很大程度上与蛋白质合成无关。胞质羧化酶ACC的行为在所有这些方面与线粒体羧化酶相同，这一观察结果与两个细胞区室中存在类似的生物素化机制一致。此外，数据支持这样的观点，即人类线粒体和胞质中全羧化酶合成酶系统的至少一些成分是共享的，并且与生物素缺乏细胞中活性恢复代表预先存在的酶蛋白生物素化的观点一致。正常细胞和婴儿期发病细胞中ACC活性的适度下降可能与该形式多种羧化酶缺乏症中观察到的表皮完整性受损有关。最后，比较了代表一系列临床严重程度的突变体细胞中的ACC和线粒体羧化酶活性。根据化学标准，临床严重程度中等的迟发性患者的细胞最终可归类为假定的全羧化酶合成酶缺陷细胞。准确的病因分类不能仅基于临床表现，所有患者都应进行生化研究。因此，我们提出了一种基于生化标准的多种羧化酶缺乏症分类方法。
