In higher plants, ADP-glucose pyrophosphorylase (AGPase) cat...

created [InstanceEdit:2960177] D'Eustachio, P, 2013-01-04
dbId 2960196
displayName In higher plants, ADP-glucose pyrophosphorylase (AGPase) cat...
literatureReference
modified [InstanceEdit:9918301] Naithani, Sushma, 2024-08-14
schemaClass Summation
text In higher plants, ADP-glucose pyrophosphorylase (AGPase) catalyzes the first committed step of starch biosynthesis by converting Alpha-D-glucose 1-phosphate (G1P) to ADP-glucose. AGPase reaction occurs in the plastid and in the cytosol of the cereal endosperm; however, ADP-glucose from the cytosol is transported to amyloplast by the ADP-glucose transporter encoded by the rice Brittle1 (OsBT1) gene. AGPase is also known as Glucose-1-phosphate adenylyltransferase. AGPase is a heterotetramer composed of two small (AGPS ) and two large (AGPL) subunits (Lee et al., 2007, and Figuera et al, 2022). The rice genome contains two genes encoding small subunits, OsAGPS1 and OsAGPS2, and four genes encoding large subunits, OsAGPL1, OsAGPL2, OsAGPL3, and OsAGPL4. OsAGPS2a (the product of the leaf-preferential transcript of OsAGPS2), and OsAGPS1, OsAGPL1, OsAGPL3, and OsAGPL4 are plastid-targeted isoforms. However, OsAGPS2b (a product of a seed-specific transcript of OsAGPS2) and OsAGPL2 are found in the cytosol (Lee et al., 2007). The rice osagps2 and osagpl2 mutants affect OsAGPL2 and OsAGPS2b, causing a shrunken endosperm due to a decrease in starch synthesis (Lee et al., 2007). On the other hand, a mutation in the plastid AGPase subunits causes disruption in root gravitropism leading to the gravitropic phenotype (Zhang et al., 2019).