PYGB
Description
The PYGB (glycogen phosphorylase B) is a protein-coding gene located on chromosome 20.
PYGB, or glycogen phosphorylase, brain, is an enzyme encoded by the PYGB gene located on chromosome 20. This enzyme is predominantly found in the brain and is responsible for the breakdown of glycogen into glucose-1-phosphate, a key step in glycogen degradation. PYGB exists as a homodimer that can associate into homotetramers, which is the active form of the enzyme. The activity of PYGB is regulated by various factors, with AMP activating the enzyme and ATP, ADP, and glucose-6-phosphate inhibiting it. PYGB shares similarities with other glycogen phosphorylase isoforms found in muscle (PYGM) and liver (PYGL), but it is distinguished by its unique structure and subcellular localization. PYGB is the largest of the three isoforms with a length of 862 residues, primarily due to its extended 3'-UTR at the C-terminal. Despite its size difference, it shares significant homology with PYGM (83%) and PYGL (80%) in amino acid sequence, suggesting a close evolutionary relationship. The high similarity in nucleotide and amino acid sequences, as well as codon usage, between PYGB and PYGM further indicates a shared evolutionary history through gene duplication and translocation. The presence of a possible pseudogene on chromosome 10 adds to the complexity of the PYGB gene.
PYGB, also known as glycogen phosphorylase, brain form, is an important allosteric enzyme in carbohydrate metabolism. It plays a crucial role in glycogen mobilization by catalyzing the breakdown of glycogen into glucose-1-phosphate. While enzymes from different sources may have varying regulatory mechanisms and substrate preferences, all known phosphorylases share fundamental catalytic and structural properties.
PYGB is also known as GPBB.
