Activity or concentration of in the level of adenylate kinase (EC 2.7.4.3) in erythrocytes below the lower limit of normal. Adenylate kinase is a ubiquitous monomeric enzyme that catalyzes the reversible conversion of MgATP plus AMP to MgADP plus ADP and contributes to homeostasis of the adenine nucleotide composition in the cell. [from
HPO]