Overlooked tools for studying soil nitrogen depolymerization: Aminopeptidase assays using nitroanilide substrates. Issue 1 (14th June 2022)

• Record Type: Journal Article
• Authors: Margenot, Andrew J; Daughtridge, Rachel C
• Is Part Of: Agricultural & environmental letters. Volume 7:Issue 1(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-06-14
• Subjects: Agriculture -- Periodicals; Agriculture -- Environmental aspects -- Periodicals; Agriculture; Agriculture -- Environmental aspects; Periodicals; 630
• DOI: 10.1002/ael2.20079
• Languages: English
• ISSNs: 2471-9625

Abstract

Abstract: Aminopeptidases are one of the extracellular hydrolytic enzymes that catalyze organic nitrogen (N) depolymerization and are commonly assayed using fluorogenic substrates. However, chromogenic substrates based on para ‐nitroaniline ( p NA) developed for the study of aminopeptidases in the 1960s have been underutilized. To gauge the use of p NA substrates to assay soil aminopeptidases, a systematic literature review was conducted. We identified 61 studies that were nearly all limited to measuring leucine and/or glycine aminopeptidases, despite the commercial availability of at least six other aminopeptidase‐specific p NA substrates. Assay parameters of scale (slurry vs. direct incubations), matrix type, buffer pH, substrate concentration, assay duration and temperature, termination, and colorimetry indicated a lack of standardization and a confusion of p NA with p NP substrates despite important differences in abiotic hydrolysis and absorbance maxima. Future studies should systematically evaluate and standardize these parameters and assess the sensitivity of other amino acid‐specific aminopeptidases to carbon (C), N, and sulfur (S) cycling. Core Ideas: Para ‐nitroaniline ( p NA)‐linked substrates are underutilized for the assays of soil aminopeptidase activities. Systematic literature review identified 61 studies, dominantly focused on leucine and glycine aminopeptidase. Lack of standardization of key assay parameters is important for comparability of aminopeptidase activities. Confusion of para ‐nitrophenol with p NA substrate methodology introduces unnecessary steps and errors. Potential of p NA substrates for study of soil aminopeptidases can be realized by standardizing assay parameters.