Effect of pH, temperature and storage time on the stability of bovine myelin basic protein

Bovine central nervous system tissue (CNT) harboring highest levels of the infectious agent for prion diseases, has been banned from food and feed supplies. Effective detection of CNT in excessively processed meat and feedstuffs requires the assay based on a stable marker in CNT as the analyte. Myelin basic protein (MBP), the major central nervous system (CNS) myelin protein, was reported to be detectable up to 115 °C in the literature. This study further investigated the effects of pH, temperature and storage time on the stability of purified bovine MBP (18.5 kDa) in solutions. Purified MBP dissolved in 10 mM PBS was adjusted to pH 3.0, 7.2 and 10.5, respectively. Sample at each pH was subjected to three heat treatments, 100 °C, 121 °C, and 133 °C for 30 min. The unheated and 100 °C heated samples at pH 7.2 were stored at 4 °C for 19 days to study the storage stability of bovine MBP. The immunoreactivity of all samples was examined using indirect non-competitive enzyme-linked immunosorbent assay and immunoblotting with an anti-MBP monoclonal antibody. The protein degradation was observed by analyzing samples using SDS-PAGE. Results show that bovine MBP was most stable at pH 7.2 while the protein was least stable at pH 10.5. MBP started to degrade after heating at 121 °C for 30 min at pH 7.2. Storage up to 19 days at 4 °C did not significantly affect the immunoreactivity of unheated and heated samples. However, unheated MBP samples started to show degradation from day 8 of storage; while no degradation was observed in 100 °C heated samples over the storage time. This study demonstrated that bovine MBP can be a suitable marker for the detection of bovine CNT in highly processed food and feed supplies.