Ofman R, Hettema E H, Hogenhout E M, Caruso U, Muijsers A O, Wanders R J
Department of Clinical Chemistry, Academic Medical Centre, University of Amsterdam, The Netherlands.
Hum Mol Genet. 1998 May;7(5):847-53. doi: 10.1093/hmg/7.5.847.
Rhizomelic chondrodysplasia punctata (RCDP) is a genetic disorder which is clinically characterized by rhizomelic shortening of the upper extremities, typical dysmorphic facial appearance, congenital contractures and severe growth and mental retardation. Patients with RCDP can be subdivided into three subgroups based on biochemical analyses and complementation studies. The largest subgroup contains patients with mutations in the PEX7 gene encoding the PTS2 receptor. This results in multiple peroxisomal abnormalities which includes a deficiency of acyl-CoA:dihydroxyacetonephosphate acyltransferase (DHAPAT), alkyl-dihydroxyacetonephosphate synthase (alkyl-DHAP synthase), peroxisomal 3-ketoacyl-CoA thiolase and phytanoyl-CoA hydroxylase, although there are differences in the extent of the deficiencies observed. Patients in the two other subgroups have been reported to be either deficient in the activity of DHAPAT (RCDP type 2) or alkyl-DHAP synthase (RCDP type 3) while no other abnormalities could be observed. To examine whether the gene encoding DHAPAT is mutated in patients with RCDP type 2, we determined the N-terminal amino acid sequence of the enzyme isolated from human placenta. Using this sequence as a query, we identified a 2040 bp open reading frame (ORF) in the human database of expressed sequence tags. Expression of this ORF in the yeast Saccharomyces cerevisiae showed that we have identified the DHAPAT cDNA. The deduced amino acid sequence revealed no PTS2 consensus sequence. In contrast DHAPAT appears to contain a putative PTS1 at the extreme C-terminus. All RCDP type 2 patients analyzed were found to contain mutations in their DHAPAT cDNA. This demonstrates that RCDP type 2 is the result of mutations in DHAPAT.
肢根型点状软骨发育不良（RCDP）是一种遗传性疾病，其临床特征为上肢肢根型短小、典型的面部畸形外观、先天性挛缩以及严重的生长和智力发育迟缓。根据生化分析和互补研究，RCDP患者可分为三个亚组。最大的亚组包含编码PTS2受体的PEX7基因突变的患者。这导致多种过氧化物酶体异常，包括酰基辅酶A：磷酸二羟丙酮酰基转移酶（DHAPAT）、烷基磷酸二羟丙酮合酶（烷基-DHAP合酶）、过氧化物酶体3-酮酰基辅酶A硫解酶和植烷酰辅酶A羟化酶缺乏，尽管观察到的缺乏程度存在差异。据报道，另外两个亚组的患者要么缺乏DHAPAT活性（RCDP 2型），要么缺乏烷基-DHAP合酶（RCDP 3型），而未观察到其他异常。为了检测编码DHAPAT的基因在RCDP 2型患者中是否发生突变，我们测定了从人胎盘中分离的该酶的N端氨基酸序列。以该序列作为查询序列，我们在人类表达序列标签数据库中鉴定出一个2040 bp的开放阅读框（ORF）。该ORF在酿酒酵母中的表达表明我们已鉴定出DHAPAT cDNA。推导的氨基酸序列未显示PTS2共有序列。相反，DHAPAT似乎在极端C端含有一个推定的PTS1。分析的所有RCDP 2型患者的DHAPAT cDNA中均发现有突变。这表明RCDP 2型是DHAPAT突变的结果。
