TIR domain. The Toll/interleukin-1 receptor (TIR) homology domain is an intracellular signalling domain found in MyD88, interleukin 1 receptor and the Toll receptor. It contains three highly-conserved regions, and mediates protein-protein interactions between the Toll-like receptors (TLRs) and signal-transduction components. TIR-like motifs are also found in plant proteins thought to be involved in resistance to disease. When activated, TIR domains recruit cytoplasmic adaptor proteins MyD88 and TOLLIP (Toll interacting protein). In turn, these associate with various kinases to set off signalling cascades.

This family is most closely related to the GT1 family of glycosyltransferases. The sucrose-phosphate synthases in this family may be unique to plants and photosynthetic bacteria. This enzyme catalyzes the synthesis of sucrose 6-phosphate from fructose 6-phosphate and uridine 5'-diphosphate-glucose, a key regulatory step of sucrose metabolism. The activity of this enzyme is regulated by phosphorylation and moderated by the concentration of various metabolites and light.

sucrose synthase. This model represents sucrose synthase, an enzyme that, despite its name, generally uses rather produces sucrose. Sucrose plus UDP (or ADP) becomes D-fructose plus UDP-glucose (or ADP-glucose), which is then available for cell wall (or starch) biosynthesis. The enzyme is homologous to sucrose phosphate synthase, which catalyzes the penultimate step in sucrose synthesis. Sucrose synthase is found, so far, exclusively in plants and cyanobacteria [Energy metabolism, Biosynthesis and degradation of polysaccharides].

Resistant to P. syringae 6; Provisional

sucrose synthase