nucleotide-binding domain (NBD) of pantothenate kinase 4 (Pank4) from type II pantothenate kinase (PanK-II) subfamily
PanK (EC 2.7.1.33), also called pantothenic acid kinase, is the first enzyme in the Coenzyme A (CoA) biosynthetic pathway. It catalyzes the phosphorylation of pantothenate (vitamin B5) to form 4'-phosphopantothenate at the expense of a molecule of adenosine triphosphate (ATP), which is the rate-limiting step in CoA biosynthesis. It cannot utilize a phosphoryl donor other than ATP. Three distinct types of PanK have been identified, PanK-I, PanK-II and PanK-III. Eukaryotic PanK-II enzymes often occur as different isoforms, such as PanK1, PanK2, PanK3 and PanK4. The model corresponds to PanK4, which is a putative bifunctional protein with a predicted amino-terminal pantothenate kinase (type II PanK) domain fused to a carboxy-terminal phosphatase domain. PanK4 homologs are found in animals, fungi, and plants. The human PanK4 kinase domain has catalytically-inactivating amino acid substitutions, thus it is characterized as a catalytically inactive pseudoPanK.
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