When blood glucose rises above 5 mM, hexokinase IV activity increases, but hexokinase I is already operating near Vmax and cannot respond to an increase in glucose concentration. 

TLS Online TPP Program

#Id: 8622

#XL - R Botany

Cyclins are degraded through the action of two different E3-ligases:

1. SCF (Skp1, Cullin, and F-box proteins) 

2. APC/C or cyclosome

TLS Online TPP Program

#Id: 8623

#XL - R Botany

SCF and APC/C are multisubunit ubiquitin-protein ligases that belong to the RING finger family of ubiquitin-protein ligases.

TLS Online TPP Program

#Id: 8625

#XL - R Botany

Human SCF complexes contain: 

Three core components - Cul1 subunit, RBX1, Skp1 

and a substrate-targeting F-box protein

TLS Online TPP Program

#Id: 8626

#XL - R Botany

RBX1 is a RING finger–containing protein that binds the E2 ubiquitin-conjugating enzyme.

TLS Online TPP Program

#Id: 8627

#XL - R Botany

phosphoserine/threonine-binding F-box protein is Skp2, which uses a series of leucine-rich repeats to bind to target proteins only when they are phosphorylated.

TLS Online TPP Program

#Id: 8628

#XL - R Botany

APC/C consists of 14 core subunits in metazoans and 13 core subunits in yeast.