Levels of the enzyme meprin-beta are raised in the brains and cerebrospinal fluid of people with Alzheimer's disease, and it is specifically the mature, active form of the protein that increases. The finding comes from the Altered Molecular Mechanism in Alzheimer's Disease and Dementia laboratory led by Javier Saez Valero at the Institute for Neurosciences, a joint centre of the Miguel Hernandez University of Elche and the Spanish National Research Council, and has been published in Alzheimer's Research & Therapy.
The relevance lies in how beta-amyloid is made. Amyloid precursor protein, or APP, is cut by several enzymes, and those cuts determine whether the beta-amyloid peptide that accumulates in Alzheimer's brains is produced. BACE1 is the beta-secretase that has drawn most of the research and drug development attention, but it is not the only enzyme capable of doing that job. Meprin-beta can also act as a beta-secretase, and the new data suggest it is not a bystander in the disease.
The distinction between forms of the enzyme is what makes the result more than a simple headcount. Meprin-beta exists in an immature, inactive state and a mature, active one, and the team measured these separately rather than lumping them together. Finding the increase concentrated in the active form points to genuinely elevated enzymatic activity rather than a harmless build-up of unprocessed protein.
For the field, this adds a second candidate to a story that has been dominated by BACE1, and one that shows up in cerebrospinal fluid as well as brain tissue - the kind of sample clinicians can actually obtain from living patients. Whether meprin-beta turns out to be useful as a marker, a drug target, or simply a piece of the amyloid puzzle will depend on work that follows from here.