Mandelli J, Wajner A, Pires R, Giugliani R, Coelho J C
Department of Biochemistry, ICBS, Federal University of Rio Grande do Sul, RS, Porto Alegre, Brazil.
Clin Chim Acta. 2001 Oct;312(1-2):81-6. doi: 10.1016/s0009-8981(01)00593-9.
Mucopolysaccharidosis type I (MPS I) is a disease caused by deficiency of the enzyme alpha-L-iduronidase (IDUA). Since no treatment is currently available for this disorder, the detection of heterozygotes is very important for genetic counseling and prenatal diagnosis. The objective of the present study was to characterize plasma IDUA from MPS I heterozygotes in an attempt to distinguish it from that of normal individuals.
We determined the optimum pH, Km, Vmax and Calpha (Vmax/Km) of the reaction and the thermal stability of IDUA at 50 degrees C.
MPS I heterozygotes can be separated from normal individuals on the basis of Km, Calpha and thermal stability of the enzyme.
Taking into consideration the clinical status of the homozygous offspring, we were able to subdivide the MPS I heterozygotes into various subgroups (Hurler, Scheie or Hurler/Scheie compound), and verified that the Hurler subgroup had a lower optimum pH for IDUA activity than controls and other MPS I subgroups, and that all MPS I subgroups had higher Km and lower Calpha when compared to controls.
I型黏多糖贮积症（MPS I）是一种由α-L-艾杜糖醛酸酶（IDUA）缺乏引起的疾病。由于目前尚无针对该疾病的治疗方法，杂合子的检测对于遗传咨询和产前诊断非常重要。本研究的目的是对MPS I杂合子的血浆IDUA进行特征分析，试图将其与正常个体的IDUA区分开来。
我们测定了该反应的最佳pH值、米氏常数（Km）、最大反应速度（Vmax）和催化常数（Calpha，即Vmax/Km）以及IDUA在50℃时的热稳定性。
MPS I杂合子可根据该酶的Km、Calpha和热稳定性与正常个体区分开来。
考虑到纯合子后代的临床状况，我们能够将MPS I杂合子细分为不同亚组（Hurler、Scheie或Hurler/Scheie复合组），并证实Hurler亚组IDUA活性的最佳pH值低于对照组和其他MPS I亚组，且与对照组相比，所有MPS I亚组的Km更高而Calpha更低。
