Glycogen phosphorylase, brain form (PYGB)

Glycogen phosphorylase, brain form (PYGB) is a critical enzyme that catalyzes the rate-limiting step in glycogenolysis, the breakdown of glycogen into glucose-1-phosphate. Although named for its prevalence in the brain, where it provides an essential energy reserve during periods of high neural activity or glucose deprivation, it is also significantly expressed in cardiac and fetal tissues [1][2]. In the context of disease, PYGB is frequently overexpressed in various malignancies, such as glioblastoma and colorectal cancer, facilitating the metabolic reprogramming necessary for tumor survival and proliferation under hypoxic conditions [3][4]. This makes it an attractive target for metabolic-based cancer therapies. Furthermore, the release of the BB isoenzyme into the bloodstream serves as a sensitive clinical biomarker for early-stage myocardial infarction and brain injury [5]. Pharmacological inhibition of PYGB, using small molecules like CP-91149, aims to disrupt these pathological energy pathways, though achieving selectivity over liver and muscle isoforms remains a significant therapeutic challenge [6].

Other names

Brain glycogen phosphorylaseGPBBPhosphorylase, glycogen; brainPYGB

Inhibition of glycogenolysis by blocking the conversion of glycogen to glucose-1-phosphate, thereby reducing glucose availability for cellular energy processes.