NAD+ kinase: molecular weight determination by low-angle laser-light scattering

Area of Science:

• Biochemistry
• Molecular Biology
• Enzymology

Background:

• NAD+ kinase (NADK) is a crucial enzyme in cellular metabolism, catalyzing the synthesis of NADP+.
• Understanding the molecular properties of NADK from different species aids in elucidating enzyme structure-function relationships.

Purpose of the Study:

• To determine the absolute molecular weight of chicken liver NAD+ kinase (NADK) using low-angle laser-light scattering (LALLS).
• To compare the molecular weight of chicken liver NADK with NADK from other species to infer potential quaternary structures.

Main Methods:

• Low-angle laser-light scattering (LALLS) was utilized to measure the weight-average molecular weight (Mw).
• The second virial coefficient was also calculated to assess protein-solvent interactions.

Main Results:

• The absolute weight-average molecular weight (Mw) of chicken liver NADK was determined to be 275,000 +/- 15,000.
• This Mw value is consistent with previously reported values for pigeon liver NADK (270,000) and C. utilis NADK (260,000).
• The calculated second virial coefficient was -1.65 X 10(-3) ml X mol X g2.

Conclusions:

• Chicken liver NADK shares a similar molecular weight with NADK from pigeon liver and C. utilis.
• If NADK functions as a dimer, the molecular weight difference suggests rabbit liver NADK (136,000) may represent an active monomer unit.