- Beta-galactosidase cleaves ONPG to produce ONP and galactose.
- The molar extinction coefficient is reported to be either 4500 M-1cm-1  or 4900 M-1cm-1  (not original references, better references would be preferable).
- Skoneczny M and Rytka J. Oxygen and haem regulate the synthesis of peroxisomal proteins: catalase A, acyl-CoA oxidase and Pex1p in the yeast Saccharomyces cerevisiae; the regulation of these proteins by oxygen is not mediated by haem. Biochem J. 2000 Aug 15;350 Pt 1:313-9.
- Onishi N and Tanaka T. Purification and properties of a novel thermostable galacto-oligosaccharide-producing beta-galactosidase from Sterigmatomyces elviae CBS8119. Appl Environ Microbiol. 1995 Nov;61(11):4026-30.