An H-ATPase Assay: Proton Pumping and ATPase Activity Determined Simultaneously in the Same Sample

Area of Science:

• Biochemistry
• Plant Physiology
• Spectrophotometry

Background:

• H(+)-ATPase is crucial for proton transport across plasma membranes.
• Measuring proton pumping and ATPase activity often requires separate assays.
• A combined assay offers a more integrated approach to study these coupled processes.

Purpose of the Study:

• To develop a continuous spectrophotometric assay for H(+)-ATPase activity.
• To simultaneously measure proton pumping and ATP hydrolysis.
• To establish a convenient method for relating ATP hydrolysis to proton pumping in plant plasma membranes.

Main Methods:

• Combined two established methods: spectrophotometric monitoring of proton uptake (acridine orange probe) and enzymatic measurement of ATP hydrolysis (NADH oxidation).
• Utilized plasma membrane vesicles from Avena sativa L. (cv Rhiannon).
• Monitored absorbance changes at 495 nm for proton pumping and 340 nm for ATPase activity.

Main Results:

• Successfully developed a continuous spectrophotometric assay for H(+)-ATPase activity.
• Demonstrated simultaneous measurement of proton uptake and ATP hydrolysis.
• Showcased the assay's convenience for correlating ATP hydrolysis with proton pumping.

Conclusions:

• The developed assay provides a convenient and integrated method for studying H(+)-ATPase function.
• This technique allows for the direct comparison of ATP hydrolysis and proton pumping activities.
• Facilitates research into the bioenergetics of plant plasma membrane transport systems.