Degradation of dissolved organic phosphorus (phosphonates): C-P lyase activity (CLA)

• Page authors: PRIMO
• Responsible curator: Hagen Buck-Wiese

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C-P lyase activity (CLA)
Approach: dansyl-labelled phosphonate substrate + HPLC fluorescence detection
Context: incubation, lab
Spatial scale: point sample
Temporal scale: hours to days
Units: mol P L-1 h-1
Community captured: heterotrophic bacteria
Co-measurements: cell abundance

Method Overview

C-P lyase is an enzyme that cleaves the carbon–phosphorus bond in phosphonate compounds (organic compounds with a direct C–P bond), releasing inorganic phosphate. It is encoded by the phnJ gene within the phn operon and is expressed by certain bacteria and cyanobacteria under phosphorus-limiting conditions. C-P lyase activity is measured using dansyl-labelled phosphonate substrate proxies, which upon C–P bond cleavage release a fluorescent dansyl-containing product. The product is separated from substrate by HPLC and quantified by fluorescence detection, and the rate of product formation is expressed as the C-P lyase activity rate.

Scale of measurement

Sampling after hours to days of incubation.

Data generated

C-P lyase activity rate (mol P L^-1 h^-1) at saturating substrate concentration. Indicates the community's capacity to access phosphonate-bound phosphorus, which constitutes a significant fraction (~25%) of dissolved organic phosphorus in some marine environments.

Units & currency

Units are mol P L^-1 h^-1. The currency is phosphorus.

Sample size

Typical samples are < 1 L in volume.

Limitations

The HPLC-based detection requires more complex sample preparation than the fluorimetric MUF assays. The synthetic dansyl-phosphonate proxy may not represent the full range of natural phosphonate substrates. Rates measured represent V_max at saturating substrate. Bottle effects may arise.

Example Applications & Protocols

Classic examples

• Granzow et al. (2021) A sensitive fluorescent assay for measuring carbon-phosphorus lyase activity in aquatic systems

Common calculations/conversions

• CLA rate (nmol P L^-1 h^-1) = HPLC peak area (product) × molar extinction coefficient / incubation time.