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MetaCyc Enzyme: galactosyltransferase / raffinose synthase

Gene: RFS Accession Number: G-9595 (MetaCyc)

Synonyms: galactinol:sucrose 6-galactosyltransferase

Species: Pisum sativum

Summary:
A raffinose synthase (RFS) was partially purified from maturing seeds of pea (Pisum sativum) [Peterbauer02]; the gene encoding this protein was cloned and the protein expressed in a baculovirus expression system. The enzyme was tested both in its non-purified form (from the crude extract of baculovirus-infected insect cells) and in its partially-purified form: the same activity was demonstrated in both systems. The enzyme catalyzes the formation of raffinose from sucrose and galactinol. In addition to galactinol, the enzyme was able to use galactosylononitol; and sucrose could be replaced by D-ononitol or D-pinitol. In the latter case, the authors of the study did not specify whether the product of the reaction was galactopinitol A, galactopinitol B or a mixture of both [Peterbauer02]. Raffinose itself could not be used as an acceptor.

Molecular Weight of Polypeptide: 88.7 kD (from nucleotide sequence)

Unification Links: Entrez:CAD20127 , Protein Model Portal:Q8VWN6 , UniProt:Q8VWN6

Relationship Links: CAZy:IN-FAMILY:GH36 , InterPro:IN-FAMILY:IPR008811 , InterPro:IN-FAMILY:IPR013785 , InterPro:IN-FAMILY:IPR017853 , Pfam:IN-FAMILY:PF05691

Gene-Reaction Schematic: ?

Gene-Reaction Schematic


Enzymatic reaction of: galactosyltransferase

EC Number: 2.4.1.-

D-ononitol + galactinol <=> D-galactosylononitol + myo-inositol

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is favored in the direction shown.


Enzymatic reaction of: raffinose synthase

EC Number: 2.4.1.82

galactinol + sucrose <=> myo-inositol + raffinose

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.

The reaction is favored in the direction shown.

Alternative Substrates for sucrose: D-pinitol [Peterbauer02 ]

In Pathways: stachyose biosynthesis

Summary:
When expressed in the insect cell-baculovirus system, crude extracts containing the recombinant protein displayed raffinose synthase activity at 0.82 pkat.mg-1 soluble protein [Peterbauer02]. The specific activity of the partially purified enzyme from maturing seeds was 75.4 pkat.mg-1 protein.

Inhibitors (Competitive): 1,5-dideoxy-1,5-imino-D-galactitol [Peterbauer02] , myo-inositol [Peterbauer02]

Inhibitors (Other): Ni2+ [Peterbauer02]

Primary Physiological Regulators of Enzyme Activity: myo-inositol

Kinetic Parameters:

Substrate
Km (μM)
Citations
galactinol
7300.0
[Peterbauer02]
sucrose
22900.0
[Peterbauer02]

pH(opt): 7.0 [Peterbauer02]


References

Peterbauer02: Peterbauer T, Mach L, Mucha J, Richter A (2002). "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." Planta 215(5);839-46. PMID: 12244450


Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by SRI International Pathway Tools version 19.0 on Fri Mar 27, 2015, biocyc13.