Glucose-6-phosphate dehydrogenase (G6PD or G6PDH) is a cytosolic enzyme in the pentose phosphate pathway, a metabolic pathway that supplies reducing energy to cells (such as erythrocytes) by maintaining the level of the co-enzyme nicotinamide adenine dinucleotide phosphate (NADPH).

Contaminants: CPK, 6-PGDH, PGI, PGM: <0,01% HK: <0,05%
Phosphoglucose Isomerase: <0,0001%
Phosphoglucomutase: <0,00001%
6-Phosphogluconate Dehydrogenase: <0,00005%
Myokinase: <0,0001%
NADH Oxidase: <0,0001%
NADPH Oxidase: <0,0001%
Glutathione Reductase:: <0,00001%
Creatine Phosphokinase: <0,00026%
Hexokinase: <0,00092%

Structure: Neither cysteine nor cystine residues is present in the enzyme molecule and essential lysine is indicated to be at active site
Inhibitors: Acyl=CoA, metal ions
Michaelis Constants : NAD+ linked: 1,06×10⁻⁴ M (NAD+), 5,27×10⁻⁵ M (G-6-P), NADP+ linked: 5,69×10⁻⁶ M (NADP+), 8,1×10⁻⁵ M (G-6-P)
Thermal stability: below 37 °C (pH 8,0, 30 min)
Extinction Coefficient (E1%)E0,1% = 1,15 (280,5 nm, 0,09 M Tris-HCl, pH 7,2)(Lit.)
Isoelectric point (pI): 4,6

Either NAD+ or NADP+ serves as coenzyme, the reaction velocity with NAD+ being approximately 1.8 times greater than with NADP+ p-Glucose-6-phosphate is a preferential substrate for the enzyme, although p-Glucose reacts slowly, Fructose-6-phosphate, fructose-1, 6-diphoshate and ribose-5-phosphate are not considered to be substrates.

Unit definition: One unit will reduce 1,0 µmole of NAD+ per minute at pH 7,8 and 25 °C.