Weed research offers insight into Alzheimer's brain chemistry

An international team of plant scientists, led by Stockholm University, has discovered a new enzyme in the common weed thale cress. The substance has an important link to the human brain chemistry responsible for turning off plaque formation in Alzheimer’s disease.

The study is the result of collaboration between biochemistry, biophysics and neurochemistry researchers at Stockholm University, SciLifeLab at the Karolinska Institute, La Trobe University and the University of Western Australia. It has been published in the Proceedings of the National Academy of Sciences.

The enzyme is a novel organelle oligopeptidase (OOP), which was found in mitochondria and chloroplasts - tiny but highly important energy generation centres in the cells of thale cress. The import of proteins into mitochondria and chloroplasts is essential for cellular function, and the small peptides which are produced following this import must be destroyed.

Biochemist Professor Jim Whelan, of La Trobe and UWA, said the OOP “destroys small peptides in the plant’s cell that would otherwise become toxic to the cell”. He says documenting the biological pathways which lead to enzymes breaking down proteins and peptides “is essential for understanding the role of proteases in disease in plants and animals”.

The enzyme presequence protease (PreP), which was also first extensively characterised in plants, has the ability to degrade the peptide beta-amyloid that forms insoluble fibres, or plaques, in the brain of Alzheimer’s patients. Professor Elzbieta Glaser of Stockholm University said the team believes “the OOP and PreP cooperate to completely break down harmful peptides that accumulate and adversely affect mitochondrial activities”.

Professor Glaser said that by studying the human variant of OOP, and examining its role in the degradation of amyloid-beta peptide, “it may be of importance for research in Alzheimer’s disease and other age-related diseases”.