UniProt functional annotation for Q5JFM9



	UniProt functional annotation for Q5JFM9

UniProt code: Q5JFM9.

Organism: Thermococcus kodakarensis (strain ATCC BAA-918 / JCM 12380 / KOD1) (Pyrococcus kodakaraensis (strain KOD1)).

Taxonomy: Archaea; Euryarchaeota; Thermococci; Thermococcales; Thermococcaceae; Thermococcus.

Function: Catalyzes the isomerization of ribose 1,5-bisphosphate (R15P) to ribulose 1,5-bisphosphate (RuBP), the CO(2) acceptor and substrate for RubisCO. Only accepts the alpha-anomer of D-ribose 1,5-bisphosphate as substrate, being inactive on the beta-anomer. Displays a strict substrate specificity, since other phosphorylated sugars such as R5P, ribose, G16P, G6P, G1P, FBP, F6P, and PRPP, are not substrates. Functions in an archaeal AMP degradation pathway, together with AMP phosphorylase and RubisCO. {ECO:0000269|PubMed:17303759, ECO:0000269|PubMed:22511789, ECO:0000269|PubMed:23065974}.

Catalytic activity: Reaction=alpha-D-ribose 1,5-bisphosphate = D-ribulose 1,5-bisphosphate; Xref=Rhea:RHEA:32243, ChEBI:CHEBI:57870, ChEBI:CHEBI:68688; EC=5.3.1.29; Evidence={ECO:0000255|HAMAP-Rule:MF_02230, ECO:0000269|PubMed:17303759, ECO:0000269|PubMed:22511789, ECO:0000269|PubMed:23065974};

Activity regulation: Is highly activated in the presence of AMP, with an increase of >40-fold in activity levels. Among other nucleotides, isomerase activity is slightly increased in the presence of GMP, but CMP, UMP, TMP, and NAD(+) have no effect; therefore, AMP is likely the major activator of R15P isomerase in vivo. To a lesser extent, various compounds with an adenosyl moiety, such as dAMP, adenosine, or methylthioadenosine, can also act as activators. The regulation of this enzyme by AMP prevents excess degradation of intracellular AMP by the archaeal AMP degradation pathway. {ECO:0000269|PubMed:23065974}.

Biophysicochemical properties: Kinetic parameters: KM=0.6 mM for D-ribose 1,5-bisphosphate (in the presence of AMP, at 85 degrees Celsius) {ECO:0000269|PubMed:23065974}; Note=kcat is 29.2 sec(-1) (in the presence of AMP, at 85 degrees Celsius).;

Subunit: Homohexamer; trimer of dimers. {ECO:0000269|PubMed:22511789}.

Induction: Up-regulated by nucleosides (at protein level). {ECO:0000269|PubMed:23065974}.

Miscellaneous: Reaction proceeds via a cis-phosphoenolate intermediate. {ECO:0000255|HAMAP-Rule:MF_02230}.

Similarity: Belongs to the eIF-2B alpha/beta/delta subunits family. R15P isomerase subfamily. {ECO:0000255|HAMAP-Rule:MF_02230, ECO:0000305}.

Annotations taken from UniProtKB at the EBI.


Organism:		Thermococcus kodakarensis (strain ATCC BAA-918 / JCM 12380 / KOD1) (Pyrococcus kodakaraensis (strain KOD1)).
Taxonomy:		Archaea; Euryarchaeota; Thermococci; Thermococcales; Thermococcaceae; Thermococcus.



Function:		Catalyzes the isomerization of ribose 1,5-bisphosphate (R15P) to ribulose 1,5-bisphosphate (RuBP), the CO(2) acceptor and substrate for RubisCO. Only accepts the alpha-anomer of D-ribose 1,5-bisphosphate as substrate, being inactive on the beta-anomer. Displays a strict substrate specificity, since other phosphorylated sugars such as R5P, ribose, G16P, G6P, G1P, FBP, F6P, and PRPP, are not substrates. Functions in an archaeal AMP degradation pathway, together with AMP phosphorylase and RubisCO. {ECO:0000269\|PubMed:17303759, ECO:0000269\|PubMed:22511789, ECO:0000269\|PubMed:23065974}.


Catalytic activity:		Reaction=alpha-D-ribose 1,5-bisphosphate = D-ribulose 1,5-bisphosphate; Xref=Rhea:RHEA:32243, ChEBI:CHEBI:57870, ChEBI:CHEBI:68688; EC=5.3.1.29; Evidence={ECO:0000255\|HAMAP-Rule:MF_02230, ECO:0000269\|PubMed:17303759, ECO:0000269\|PubMed:22511789, ECO:0000269\|PubMed:23065974};
Activity regulation:		Is highly activated in the presence of AMP, with an increase of >40-fold in activity levels. Among other nucleotides, isomerase activity is slightly increased in the presence of GMP, but CMP, UMP, TMP, and NAD(+) have no effect; therefore, AMP is likely the major activator of R15P isomerase in vivo. To a lesser extent, various compounds with an adenosyl moiety, such as dAMP, adenosine, or methylthioadenosine, can also act as activators. The regulation of this enzyme by AMP prevents excess degradation of intracellular AMP by the archaeal AMP degradation pathway. {ECO:0000269\|PubMed:23065974}.
Biophysicochemical properties:		Kinetic parameters: KM=0.6 mM for D-ribose 1,5-bisphosphate (in the presence of AMP, at 85 degrees Celsius) {ECO:0000269\|PubMed:23065974}; Note=kcat is 29.2 sec(-1) (in the presence of AMP, at 85 degrees Celsius).;
Subunit:		Homohexamer; trimer of dimers. {ECO:0000269\|PubMed:22511789}.
Induction:		Up-regulated by nucleosides (at protein level). {ECO:0000269\|PubMed:23065974}.
Miscellaneous:		Reaction proceeds via a cis-phosphoenolate intermediate. {ECO:0000255\|HAMAP-Rule:MF_02230}.
Similarity:		Belongs to the eIF-2B alpha/beta/delta subunits family. R15P isomerase subfamily. {ECO:0000255\|HAMAP-Rule:MF_02230, ECO:0000305}.