A New Activity Assay Method for Diamine Oxidase Based on Matrix-Assisted Laser Desorption/Ionization Time-of-Flight...

Area of Science:

• Biochemistry
• Enzymology

Background:

• Copper-containing diamine oxidases (CAOs) are vital enzymes involved in cell growth, programmed cell death, and stress responses.
• Their natural substrates include putrescine, spermidine, and histamine.
• Current enzymatic activity assays rely on spectrophotometric, electrochemical, or fluorometric methods.

Purpose of the Study:

• To develop a novel method for measuring CAO activity using MALDI-TOF mass spectrometry.
• To determine kinetic parameters (kcat and Km) for substrate oxidative deamination.
• To compare the new method's accuracy and efficiency against established spectrophotometric techniques.

Main Methods:

• Purified CAO from pea (Pisum sativum) seedlings was used.
• MALDI-TOF MS was employed, utilizing α-cyano-4-hydroxycinnamic acid matrix with cetrimonium bromide.
• Activity was measured by the signal intensity ratio of product to product-plus-substrate, with correction factors applied.

Main Results:

• The MALDI-TOF MS method provided accurate results comparable to spectrophotometry.
• Kinetic parameters (kcat, Km) were successfully determined for selected substrates.
• The method demonstrated low sample consumption and rapid serial measurement capabilities.

Conclusions:

• MALDI-TOF MS offers a viable and accurate alternative for assaying copper-containing diamine oxidase activity.
• This method is advantageous for its speed, low sample requirement, and applicability in assays with spectrophotometric interference.
• The findings contribute to a better understanding of CAO kinetics and assay methodologies.