This family consists of several raffinose synthase proteins, also known as seed imbibition (Sip1) proteins. Raffinose (O-alpha- D-galactopyranosyl- (1-->6)- O-alpha- D-glucopyranosyl-(1<-->2)- O-beta- D-fructofuranoside) is a widespread oligosaccharide in plant seeds and other tissues. Raffinose synthase (EC:2.4.1.82) is the key enzyme that channels sucrose into the raffinose oligosaccharide pathway [1]. Raffinose family oligosaccharides (RFOs) are ubiquitous in plant seeds and are thought to play critical roles in the acquisition of tolerance to desiccation and seed longevity. Raffinose synthases are alkaline alpha-galactosidases and are solely responsible for RFO breakdown in germinating maize seeds, whereas acidic galactosidases appear to have other functions [2]. Glycoside hydrolase family 36 can be split into 11 families, GH36A to GH36K [3]. This family includes enzymes from GH36C.

1: Functional expression of a cDNA encoding pea (Pisum sativum L.) raffinose synthase, partial purification of the enzyme from maturing seeds, and steady-state kinetic analysis of raffinose synthesis. Peterbauer T, Mach L, Mucha J, Richter A; Planta 2002;215:839-846. PMID:12244450

2: Enzymatic breakdown of raffinose oligosaccharides in pea seeds. Blochl A, Peterbauer T, Hofmann J, Richter A; Planta. 2008;228:99-110. PMID:18335235

3: Hierarchical classification of glycoside hydrolases. Naumoff DG; Biochemistry (Mosc). 2011;76:622-635. PMID:21639842