PYGB
Glycogen phosphorylase, brain (PYGB, GPBB), is an
glucose-6-phosphate. This enzyme catalyzes the rate-determining step in glycogen degradation. [provided by RefSeq, Jul 2008][1]
Structure
The PYGB gene encodes one of three major glycogen phosphorylase
C-terminal. Nonetheless, it shares high homology in amino acid sequence with the other two isozymes, with 83% similarity with PYGM and 80% similarity with PYGL. Moreover, both its nucleotide and amino acid sequences and its codon usage share higher similarity with those of PYGM, thus indicating that the two share a closer evolutionary descent by gene duplication and translocation of a common ancestral gene. A possible pseudogene can be found on chromosome 10.[2]
Function
As a glycogen phosphorylase, GPBB catalyzes the
cardiomyocytes and at low levels in other adult and fetal tissues.[2][7][4] These other tissues also express PYGL and PYGM, but the purpose of expressing multiple glycogen phosphorylases remains unclear.[4] Nuclear localization was also cited for GPBB in gastrointestinal cancer.[8]
Clinical significance
Cancer
GPBB overexpression has been associated with several
non-small cell lung cancer (NSCLC).[3][5][8] Since GPBB is upregulated during the potential transition of adenoma cells into carcinoma cells, GPBB may be a useful biomarker to detect malignancy potential in precancerous lesions.[3]
Ischemia
Since GPBB is released from the SR membrane under
coronary artery bypass grafting. Meanwhile, GPBB levels are elevated in patients with hypertrophic cardiomyopathy.[6]
See also
References