Cytochrome b5 reductase 1, also known as CYB5R1, belongs to the flavoprotein pyridine nucleotide cytochrome reductase family. This protein is involved in desaturation and elongation of fatty acids, cholesterol biosynthesis, drug metabolism, and, in erythrocyte, methemoglobin reduction. Recombinant human CYB5R1 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.