Van Kuilenburg André B P, Meinsma Rutger, Beke Eva, Bobba Barbara, Boffi Patrizia, Enns Gregory M, Witt David R, Dobritzsch Doreen
Academic Medical Center, University of Amsterdam, Emma Children's Hospital and Department of Clinical Chemistry, P.O. Box 22700, NL-1100 DE Amsterdam, The Netherlands.
Biol Chem. 2005 Apr;386(4):319-24. doi: 10.1515/BC.2005.038.
Dihydropyrimidine dehydrogenase (DPD) is the initial and rate-limiting enzyme in the catabolism of the pyrimidine bases uracil and thymine, as well as of the widely used chemotherapeutic drug 5-fluorouracil (5FU). Analysis of the DPD gene ( DPYD ) in two patients presenting with complete DPD deficiency and the parents of an affected child showed the presence of three novel mutations, including one splice site mutation IVS11 + 1G-->T and the missense mutations 731A-->C (E244V) and 1651G-->A (A551T). The G-->T mutation in the invariant GT splice donor site flanking exon 11 (IVS11 + 1G-->T) created a cryptic splice site within exon 11. As a consequence, a 141-bp fragment encoding the aminoacid residues 400-446 of the primary sequence of the DPD protein was missing in the mature DPD mRNA. Analysis of the crystal structure of pig DPD suggested that the E244V mutation might interfere with the electron flow between NADPH and the pyrimidine binding site of DPD. The A551T point mutation might prevent binding of the prosthetic group FMN and affect folding of the DPD protein. The identification of these novel mutations in DPYD will allow the identification of patients with an increased risk of developing severe 5FU-associated toxicity.
二氢嘧啶脱氢酶（DPD）是嘧啶碱基尿嘧啶和胸腺嘧啶以及广泛使用的化疗药物5-氟尿嘧啶（5FU）分解代谢中的初始限速酶。对两名表现为完全DPD缺乏症的患者以及一名患病儿童的父母进行的DPD基因（DPYD）分析显示存在三个新突变，包括一个剪接位点突变IVS11 + 1G→T以及错义突变731A→C（E244V）和1651G→A（A551T）。外显子11侧翼的不变GT剪接供体位点中的G→T突变（IVS11 + 1G→T）在外显子11内产生了一个隐蔽剪接位点。结果，成熟的DPD mRNA中缺少一个编码DPD蛋白一级序列中氨基酸残基400 - 446的141 bp片段。对猪DPD晶体结构的分析表明，E244V突变可能会干扰NADPH与DPD嘧啶结合位点之间的电子流动。A551T点突变可能会阻止辅基FMN的结合并影响DPD蛋白的折叠。在DPYD中鉴定出这些新突变将有助于识别发生严重5FU相关毒性风险增加的患者。
