Vettenranta K, Raivio K O
Children's Hospital, University of Helsinki, Finland.
Biol Neonate. 1990;58(6):311-7. doi: 10.1159/000243285.
The activities and kinetic parameters of 5'-nucleotidase, adenosine monophosphate (AMP) deaminase, and hypoxanthine/guanine phosphoribosyltransferase (HGPRT) were assayed in human fetal brain and liver. The apparent activity of 5'-nucleotidase decreases in the liver and increases in the brain with gestation. Its apparent Km is about 27 microM for AMP in the brain at term and liver throughout gestation but about 60 microM in the premature brain. The activity of (AMP) deaminase in the liver increases, while that in the brain does not significantly change with gestation. Its apparent Km for AMP is about 5 mM in the tissues studied. The activity of HGPRT increases with gestation in both the fetal brain and liver, and is altogether high in the fetal brain. Its apparent Km for hypoxanthine appears to be high, about 59 microM, in the tissues studied. The activities measured reflect the maximal capacities of the enzymes. Conclusions concerning their in vivo activities cannot, however, be based on studies employing disrupted cells.
对人胎脑和肝脏中的5'-核苷酸酶、单磷酸腺苷（AMP）脱氨酶以及次黄嘌呤/鸟嘌呤磷酸核糖基转移酶（HGPRT）的活性和动力学参数进行了测定。5'-核苷酸酶的表观活性在肝脏中随孕期降低，而在大脑中随孕期升高。足月时大脑中AMP的表观Km约为27微摩尔，整个孕期肝脏中的表观Km约为27微摩尔，但早产大脑中的表观Km约为60微摩尔。肝脏中（AMP）脱氨酶的活性增加，而大脑中的活性随孕期无显著变化。在所研究的组织中，其对AMP的表观Km约为5毫摩尔。HGPRT的活性在胎儿大脑和肝脏中均随孕期增加，且在胎儿大脑中总体较高。在所研究的组织中，其对次黄嘌呤的表观Km似乎较高，约为59微摩尔。所测得的活性反映了这些酶的最大能力。然而，关于它们体内活性的结论不能基于使用破碎细胞的研究。
