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Blood, 1 December 2003, Vol. 102, No. 12, pp. 4198-4205. Prepublished online as a Blood First Edition Paper on August 7, 2003; DOI 10.1182/blood-2002-11-3388.
RED CELLS Erythroid pyrimidine 5'-nucleotidase: cloning, developmental expression, and regulation by cAMP and in vivo hypoxiaFrom the Physiologisches Institut, Universität Regensburg, Regensburg, Germany.
A characteristic process of terminal erythroid differentiation is the degradation of ribosomal RNA into mononucleotides. The pyrimidine mononucleotides can be dephosphorylated by pyrimidine 5'-nucleotidase (P5N-I). In humans, a lack of this enzyme causes hemolytic anemia with ribosomal structures and trinucleotides retained in the red blood cells (RBCs). Although the protein/nucleotide sequence of P5N-I is known in mammals, the onset and regulation of P5N-I during erythroid maturation is unknown. However, in circulating chicken embryonic RBCs, the enzyme is induced together with carbonic anhydrase (CAII) and 2,3-bisphosphoglycerate (2,3-BPG) by norepinephrine (NE) and adenosine, which are released by the embryo under hypoxic conditions. Here, we present the chicken P5N-I sequence and the gene expression of P5N-I during RBC maturation; the profile of gene expression follows the enzyme activity with a rise between days 13 and 16 of embryonic development. The p5n-I expression is induced (1) in definitive but not primitive RBCs by stimulation of
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| Copyright © 2003 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||
-adrenergic/adenosine receptors, and (2) in definitive RBCs by hypoxic incubation of the chicken embryo. Since embryonic RBCs increase their hemoglobin-oxygen affinity by degradation of nucleotides such as uridine triphosphate (UTP) and cytidine triphosphate (CTP), the induction of p5n-I expression can be seen as an adaptive response to hypoxia. (Blood. 2003;102:4198-4205) 
