p23_like domain found in NAD(P)H cytochrome b5 (NCB5) oxidoreductase (OR) and similar proteins. NCB5OR is widely expressed in human organs and tissues and is localized in the ER (endoplasmic reticulum). It appears to play a critical role in maintaining viable pancreatic beta cells. Mice homozygous for a targeted knockout (KO) of the gene encoding NCB5OR develop an early-onset nonautoimmune diabetes phenotype with a non-inflammatory beta-cell deficiency. The role of NCB5OR in beta cells may be in maintaining or regulating their redox status. Proteins in this group in addition contain an N-terminal cytochrome b5 domain and a C-terminal cytochrome b5 oxidoreductase domain. The gene encoding NCB5OR has been considered as a positional candidate for type II diabetes and other diabetes subtypes related to B-cell dysfunction, however variation in its coding region does not appear not to be a major contributor to the pathogenesis of these diseases.