title: Determination of arginine catabolism by salivary pellet.
abstract: To determine the formation of ammonium from arginine by oral bacteria residing in saliva and dental plaque, an arginolytic activity assay based on the work described by Nascimento et al. [2] was developed. Following the original methodology, insufficient ammonium production could be determined. To improve the method for our research goal, the following modifications were made to the original protocols:•The following changes were made to the arginine catabolism assay resulting in a 1000-fold increase in sensitivity: (i) the salivary pellet was washed and concentrated five times resulting in the removal of low density compounds interfering with the assay, (ii) the pH of the Tris-maleate buffer was increased from 6.0 to 7.5 resulting in a better conversion of arginine to ammonium and (iii) the incubation time was increased to 3 h to ensure that non-responders and salivary pellets low in cell numbers could yield detectable levels of ammonium.•Removal of a centrifuge step from the protein determination resulted in a higher protein yield improving the accuracy of the assay.•Changing from the use of the toxic, environmentally hazardous, mercury containing Nessler's reagent to a colorimetric enzyme assay achieved a safer and greener determination of ammonium concentration.
authors.affiliation: Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and Free University Amsterdam, Department of Preventive Dentistry, Gustav Mahlerlaan 3004, 1081 LA Amsterdam, The Netherlands.
authors.forename: M A
authors.initials: MA
authors.lastname: Hoogenkamp
authors.affiliation: Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and Free University Amsterdam, Department of Preventive Dentistry, Gustav Mahlerlaan 3004, 1081 LA Amsterdam, The Netherlands.
authors.forename: J M
authors.initials: JM
authors.lastname: Ten Cate
keywords: Ammonium; Arginine; Arginolytic; Arginolytic activity assay in saliva; Oral bacteria; Salivary pellet