IMPAD1 hydrolyses PAP to AMP

Sulfur is an essential element in all lifeforms used in the synthesis of sulfur-containing amino acids, maintenance of cellular redox states and detoxifying toxic compounds. 3'-phosphoadenosine 5'-phosphosulfate (PAPS) is the active form of sulfur used in these reactions, which consume PAPS, producing 3'-phosphoadenosine 5'-phosphate (PAP). PAP is degraded to 5′-AMP (AMP) by 3′-nucleotidase family. Mammals encode two 3′-nucleotidases, the Golgi-resident inositol monophosphatase 3 (IMPAD3 aka PAP phosphatase, gPAPP) and the cytosolic bisphosphate 3′-nucleotidase 1 (BPNT1, described in its own reaction). Both require Mg2+ as cofactor and both are inhibited by lithium (Hudson et al. 2013).

硫元素是生命体系中不可或缺的元素，其在硫含氨基酸的合成、维持细胞氧化还原状态以及解毒有毒化合物中发挥着重要作用。3'-磷酸腺苷5'-磷酸硫酸盐（PAPS）是参与这些反应的硫元素活性形式，这些反应消耗PAPS，产生3'-磷酸腺苷5'-磷酸（PAP）。PAP通过3′-核苷酸酶家族降解为5′-腺苷酸（AMP）。哺乳动物编码两种3′-核苷酸酶，即定位于高尔基体的肌醇单磷酸酶3（IMPAD3，又称PAP磷酸酶，gPAPP）和细胞质双磷酸3′-核苷酸酶1（BPNT1，其反应特性已单独描述）。这两种酶均需Mg2+作为辅因子，且均受锂抑制（Hudson等人，2013年）。