Hershfield M S, Francke U
Science. 1982 May 14;216(4547):739-42. doi: 10.1126/science.7079734.
Human-Chinese hamster cell hybrids and a monoclonal antibody to human S-adenosylhomocysteine hydrolase were used to identify chromosome 20 as the location of the human gene for this enzyme. The gene for adenosine deaminase had previously been mapped to this chromosome. The activity of S-adenosylhomocysteine hydrolase is dependent in vivo on that of adenosine deaminase, since the substrates for the deaminase, adenosine and deoxyadenosine, respectively, inhibit and inactivate S-adenosylhomocysteine hydrolase in genetic or drug-induced adenosine deaminase deficiency. This functional dependence and the likelihood that S-adenosylhomocysteine hydrolase, a eukaryotic enzyme, arose later than adenosine deaminase, which occurs in prokaryotes as well as eukaryotes, suggest that the occurrence of their genes on the same chromosome may have evolutionary significance. In addition, the unusual capacity of S-adenosylhomocysteine hydrolase to form stable complexes with adenosine and its cofactor, nicotinamide adenine dinucleotide, suggest that evolution of its gene may have involved recombination of a portion of the adenosine deaminase gene with an adenine nucleotide domain-coding sequence of another preexisting gene.
利用人-中国仓鼠细胞杂种和一种针对人S-腺苷同型半胱氨酸水解酶的单克隆抗体，将20号染色体确定为该酶人类基因的位置。腺苷脱氨酶基因此前已定位到这条染色体上。S-腺苷同型半胱氨酸水解酶的活性在体内依赖于腺苷脱氨酶的活性，因为在遗传性或药物诱导的腺苷脱氨酶缺乏症中，脱氨酶的底物腺苷和脱氧腺苷分别抑制并使S-腺苷同型半胱氨酸水解酶失活。这种功能依赖性以及真核酶S-腺苷同型半胱氨酸水解酶可能比腺苷脱氨酶出现得晚（腺苷脱氨酶存在于原核生物和真核生物中）这一可能性，表明它们的基因出现在同一条染色体上可能具有进化意义。此外，S-腺苷同型半胱氨酸水解酶与腺苷及其辅因子烟酰胺腺嘌呤二核苷酸形成稳定复合物的特殊能力，表明其基因的进化可能涉及腺苷脱氨酶基因的一部分与另一个预先存在的基因的腺嘌呤核苷酸结构域编码序列的重组。
