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MetaCyc Enzyme: phlorisobutyrophenone synthase / phlorisovalerophenone synthase

Gene: VPS Accession Number: G-9298 (MetaCyc)

Synonyms: CHSL, 3-methyl-1-(trihydroxyphenyl)butan-1-one synthase

Species: Humulus lupulus

Subunit composition of phlorisobutyrophenone synthase / phlorisovalerophenone synthase = [VPS]2
         phlorisovalerophenone synthase = VPS

Summary:
An enzyme was isolated from the glands of hop (Humulus lupulus) inflorescences and cones. This enzyme was purified to homogeneity and shown to catalyze the formation of phlorisovalerophenone and phlorisobutyrophenone from the condensation of malonyl-CoA with isovaleryl-CoA and isobutyryl-CoA, respectively. Although the enzyme can use both substrates as starter molecules, it does show a preference for isovaleryl-CoA [Paniego99]. A more recent study also showed that the condensation of malonyl-CoA with isovaleryl-CoA also led to the formation of 6-isobutyl-4-hydroxy-2-pyrone, and 6-(4-methyl-2-oxopentyl)-4-hydroxy-2-pyrone [Okada04a]. Additionally, when p-coumaryl-CoA is used as start substrate instead of isovaleryl-CoA, the enzyme was also shown to produce p-coumaroyltriacetic acid lactone [Okada04a]. Although the initial study describing the enzyme did provide a partial protein sequence, it is only in a later study that the gene encoding the enzyme was isolated [Okada01]. The enzyme appears to be formed of a homodimer.

Molecular Weight of Polypeptide: 43.079 kD (from nucleotide sequence), 45 kD (experimental) [Paniego99 ]

Molecular Weight of Multimer: 110 kD (experimental) [Paniego99]

pI: 6.1 [Paniego99]

Unification Links: Entrez:BAA29039 , ModBase:O80400 , Protein Model Portal:O80400 , SMR:O80400 , Swiss-Model:O80400 , UniProt:O80400

Relationship Links: Entrez-Nucleotide:PART-OF:AB015430 , InterPro:IN-FAMILY:IPR001099 , InterPro:IN-FAMILY:IPR011141 , InterPro:IN-FAMILY:IPR012328 , InterPro:IN-FAMILY:IPR016038 , InterPro:IN-FAMILY:IPR016039 , InterPro:IN-FAMILY:IPR018088 , Pfam:IN-FAMILY:PF00195 , Pfam:IN-FAMILY:PF02797 , Prosite:IN-FAMILY:PS00441

Gene-Reaction Schematic: ?


Enzymatic reaction of: 6-isobutyl-4-hydroxy-2-pyrone synthase (phlorisobutyrophenone synthase / phlorisovalerophenone synthase)

EC Number: 2.3.1.-

isovaleryl-CoA + 2 malonyl-CoA + H+ <=> 6-isobutyl-4-hydroxy-2-pyrone + 2 CO2 + 3 coenzyme A

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.

Reversibility of this reaction is unspecified.


Enzymatic reaction of: 6-(4-methyl-2-oxopentyl)-4-hydroxy-2-pyrone synthase (phlorisobutyrophenone synthase / phlorisovalerophenone synthase)

EC Number: 2.3.1.-

isovaleryl-CoA + 3 malonyl-CoA + 2 H+ <=> 6-(4-methyl-2-oxopentyl)-4-hydroxy-2-pyrone + 3 CO2 + 4 coenzyme A

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.

Reversibility of this reaction is unspecified.


Enzymatic reaction of: p-coumaroyltriacetic acid lactone synthase (phlorisobutyrophenone synthase / phlorisovalerophenone synthase)

EC Number: 2.3.1.-

4-coumaryl-CoA + 3 malonyl-CoA + 2 H+ <=> p-coumaroyltriacetic acid lactone + 3 CO2 + 4 coenzyme A

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: phlorisobutyrophenone synthase

EC Number: 2.3.1.156

3 malonyl-CoA + isobutanoyl-CoA + 3 H+ <=> phlorisobutyrophenone + 3 CO2 + 4 coenzyme A

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.

In Pathways: bitter acids biosynthesis , cohumulone biosynthesis

Kinetic Parameters:

Substrate
Km (μM)
Citations
malonyl-CoA
33.0
[Paniego99]
isobutanoyl-CoA
10.0
[Paniego99]

pH(opt): 7 [Paniego99]


Enzymatic reaction of: phlorisovalerophenone synthase

EC Number: 2.3.1.156

isovaleryl-CoA + 3 malonyl-CoA + 3 H+ <=> phlorisovalerophenone + 3 CO2 + 4 coenzyme A

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.

In Pathways: bitter acids biosynthesis , humulone biosynthesis

Kinetic Parameters:

Substrate
Km (μM)
Citations
malonyl-CoA
33.0
[Paniego99]
isovaleryl-CoA
4.0
[Paniego99]

pH(opt): 7 [Paniego99]


References

Okada01: Okada Y, Ito K (2001). "Cloning and analysis of valerophenone synthase gene expressed specifically in lupulin gland of hop (Humulus lupulus L.)." Biosci Biotechnol Biochem 65(1);150-5. PMID: 11272819

Okada04a: Okada Y, Sano Y, Kaneko T, Abe I, Noguchi H, Ito K (2004). "Enzymatic reactions by five chalcone synthase homologs from hop (Humulus lupulus L.)." Biosci Biotechnol Biochem 68(5);1142-5. PMID: 15170123

Paniego99: Paniego NB, Zuurbier KW, Fung SY, van der Heijden R, Scheffer JJ, Verpoorte R (1999). "Phlorisovalerophenone synthase, a novel polyketide synthase from hop (Humulus lupulus L.) cones." Eur J Biochem 262(2);612-6. PMID: 10336650


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 18.5 on Sun Dec 21, 2014, biocyc14.