Fujita H, Kondo M, Taketani S, Nomura N, Furuyama K, Akagi R, Nagai T, Terajima M, Galbraith R A, Sassa S
Tohoku University School of Medicine, Sendai, Japan.
Hum Mol Genet. 1994 Oct;3(10):1807-10. doi: 10.1093/hmg/3.10.1807.
Hereditary coproporphyria (HCP) is an acute hepatic porphyria with autosomal dominant inheritance, but with a variable degree of clinical expression. Molecular cloning, sequencing and expression of the defective gene for coproporphyrinogen oxidase (CPO) in a patient with HCP were carried out. Enzyme assays revealed that CPO activity in EBV-transformed lymphoblastoid cells from the proband and one of her sisters was approximately 50% of normal. Nucleotide sequence analysis of CPO cDNAs isolated from the proband's cells demonstrated three base substitutions, and three accompanying amino acid substitutions. An A514-->C transition causing a Asn172-->His substitution occurred in one allele, while two other transitions, G265-->A and G580-->A, caused Gly89-->Ser and Val194-->Ile substitutions, respectively, in the other allele. The A514-->C and the G580-->A transitions are known genetic polymorphisms. Transfection of CPO cDNA into Escherichia coli demonstrated that cDNA with the G265-->A transition produced a protein with less than 5% of normal enzyme activity. These findings indicate that the G265-->A transition, involving the highly conserved glycine residue at the 89th position, is responsible for the CPO defect in the patient and accounts for the partial deficiency of CPO activity in this pedigree.
遗传性粪卟啉原卟啉病（HCP）是一种常染色体显性遗传的急性肝卟啉病，但临床表现程度各异。对一名HCP患者的粪卟啉原氧化酶（CPO）缺陷基因进行了分子克隆、测序及表达研究。酶活性检测显示，先证者及其一名姐妹的EB病毒转化淋巴母细胞中的CPO活性约为正常水平的50%。对从先证者细胞中分离出的CPO cDNA进行核苷酸序列分析，发现了三个碱基替换以及三个相应的氨基酸替换。一个等位基因发生了A514→C转换，导致Asn172→His替换，而另一个等位基因发生了另外两个转换，即G265→A和G580→A，分别导致Gly89→Ser和Val194→Ile替换。A514→C和G580→A转换是已知的基因多态性。将CPO cDNA转染至大肠杆菌表明，发生G265→A转换的cDNA产生的蛋白质酶活性低于正常水平的5%。这些发现表明，涉及第89位高度保守甘氨酸残基的G265→A转换是导致该患者CPO缺陷的原因，也是此家系中CPO活性部分缺乏的原因。
