BLMH (bleomycin hydrolase) is a cysteine aminopeptidase with two primary functions: inactivating the chemotherapy drug bleomycin and detoxifying homocysteine thiolactone 1. The enzyme catalyzes hydrolysis of bleomycin's carboxamide bond, protecting both normal and malignant cells from drug toxicity 2. Additionally, BLMH metabolizes homocysteine thiolactone, preventing N-homocysteinylation of proteins that compromises their function 3. Mechanistically, BLMH interacts with the Phf8/H4K20me1/mTOR/autophagy pathway and amyloid precursor protein (AβPP) 1. BLMH deletion in mice causes downregulation of Phf8 and autophagy markers (Becn1, Atg5, Atg7) while upregulating mTOR and AβPP, leading to amyloid-β accumulation 1. Elevated homocysteine thiolactone metabolites in Blmh-deficient mice recapitulate these biochemical changes 1. Disease relevance is substantial: BLMH is attenuated in Alzheimer's disease brains, and Blmh deletion worsens cognitive and neuromotor deficits in 5xFAD AD models 1. BLMH variants influence bleomycin-induced pulmonary toxicity in Hodgkin lymphoma patients 4. Additionally, serum BLMH levels serve as a potential biomarker for predicting deep brain stimulation responses in Parkinson's disease 5. Clinically, BLMH characterization enables optimization of bleomycin pharmacokinetics and identification of patients requiring alternative therapies 4.