The mouse Nudt7 gene encodes a peroxisomal nudix hydrolase specific for coenzyme A and its derivatives

Abstract

A mouse homologue of the Saccharomyces cerevisiae Pcd1p coenzyme A diphosphatase, NUDT7alpha, has been expressed as a thioredoxin fusion protein in Escherichia coli. NUDT7alpha is also a CoA diphosphatase of the nudix hydrolase family, and hydrolyses CoA, CoA esters and oxidized CoA with similar efficiences, yielding 3',5'-ADP and the corresponding 4'-phosphopantetheine derivative as products. K(m) and k(cat) values with CoA were 240 microM and 3.8 s(-1). Activity was optimal at pH 8.0 with 5 mM Mg(2+) or Mn(2+) ions, while fluoride was inhibitory with an IC(50) value of 20 microM. Expression of the Nudt7 gene was highest in liver, intermediate in lung and kidney, and lowest in brain and heart, producing a 1.5 kb transcript. A similar pattern of expression was found for the human orthologue, NUDT7. An enzymically inactive splice variant, NUDT7beta, which lacks 20 amino acids downstream of the nudix motif, was also found to be expressed in mouse tissues. Transfection of HeLa cells with a vector expressing the Nudt7alpha gene fused to the C-terminus of red fluorescent protein showed that NUDT7alpha, like Pcd1p, was a peroxisomal enzyme. The function of the NUDT7 enzyme may be the elimination of oxidized CoA from peroxisomes, or the regulation of CoA and acyl-CoA levels in this organelle in response to metabolic demand.

Deregulated coenzyme A, loss of metabolic flexibility and diabetes

“…Liver and skeletal muscle from Lep −/− animals in the fed state contain almost twice the amount of CoA found in nonobese ( Lep +/+ or Lep +/− ) littermate controls [24]. The abnormally high liver CoA content results from higher PanK activity and reduced CoA degradation through Nudt7, a nudix hydrolase that specifically degrades CoA [25]. Nudt7 expression is significantly reduced in fed Lep −/− livers.…”

Excess coenzyme A reduces skeletal muscle performance and strength in mice overexpressing human PANK2

“…PanK activity is regulated through feedback inhibition by CoA and acyl-CoAs, providing a key mechanism to modulate CoA synthesis and maintain cellular CoA homeostasis (5–7). The steady state levels of tissue CoA can also be affected by degradation, but CoA-degrading enzymes have a narrow tissue distribution as they are predominantly expressed in liver and kidneys (8,9). Mammals contain four active PanK isoforms, PanK1α, PanK1β, PanK2 and PanK3 (1), which provide some functional redundancy.…”

Correction of a genetic deficiency in pantothenate kinase 1 using phosphopantothenate replacement therapy

“…If this is correct, all intracellular Ppan will be efficiently and completely converted to CoA. However, if PanK is not the sole regulatory point in the pathway or if CoA degradation via nudix hydrolases plays a determinant role [18–20], then bypassing PanK may not have the desired impact on elevating CoA levels. Phosphorylated metabolic intermediates such as Ppan cannot be delivered to cells without chemical modification due to their instability in systemic circulation and limited cell membrane permeability.…”