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Literature summary extracted from

  • Madina, B.R.; Sharma, L.K.; Chaturvedi, P.; Sangwan, R.S.; Tuli, R.
    Purification and physico-kinetic characterization of 3beta-hydroxy specific sterol glucosyltransferase from Withania somnifera (L) and its stress response (2007), Biochim. Biophys. Acta, 1774, 392-402.
    View publication on PubMed

Activating Compound

EC Number Activating Compound Comment Organism Structure
2.4.1.173 Triton X-100 up to 0.03% Triton X-100 in the assay mixture, the catalytic activity is enhanced Withania somnifera

Inhibitors

EC Number Inhibitors Comment Organism Structure
2.4.1.173 Co2+ strongly inhibits the sterol glucosyltransferase activity, IC50 (mM): 1.3 Withania somnifera
2.4.1.173 GTP the inhibitory effect of GTP is less prominent as compared to UDP Withania somnifera
2.4.1.173 Hg2+ strongly inhibits the sterol glucosyltransferase activity, IC50 (mM): 0.5 Withania somnifera
2.4.1.173 iodoacetamide strong and irreversible inhibition by thiol directed reagents like 4-chloromercuribenzoate, N-methylmaleimide and iodoacetamide suggest the requirement of free-SH groups for the catalytic activity Withania somnifera
2.4.1.173 N-ethylmaleimide strong and irreversible inhibition by thiol directed reagents like 4-chloromercuribenzoate, N-methylmaleimide and iodoacetamide suggest the requirement of free-SH groups for the catalytic activity Withania somnifera
2.4.1.173 Ni2+ strongly inhibits the sterol glucosyltransferase activity, IC50 (mM): 1.2 Withania somnifera
2.4.1.173 p-chloromercuribenzoate strong and irreversible inhibition by thiol directed reagents like 4-chloromercuribenzoate, N-methylmaleimide and iodoacetamide suggest the requirement of free-SH groups for the catalytic activity Withania somnifera
2.4.1.173 Triton X-100 at higher levels (0.3%), Triton X-100 inactivats the enzyme, giving 10% of the original activity after 30 min pre-incubation Withania somnifera
2.4.1.173 UDP the inhibitory effect of UTP and GTP is less prominent as compared to UDP Withania somnifera
2.4.1.173 UTP the inhibitory effect of UTP is less prominent as compared to UDP Withania somnifera
2.4.1.173 Zn2+ strongly inhibits the sterol glucosyltransferase activity, IC50 (mM): 0.04 Withania somnifera

KM Value [mM]

EC Number KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
2.4.1.173 0.002
-
 diosgenin for the cytosolic enzyme Withania somnifera
2.4.1.173 0.005
-
 pregnenolone for the cytosolic enzyme Withania somnifera
2.4.1.173 0.005
-
 beta-sitosterol for the cytosolic enzyme Withania somnifera
2.4.1.173 0.006
-
 3-beta-hydroxy-pregna-5,16-dien-20-one for the cytosolic enzyme Withania somnifera
2.4.1.173 0.014
-
 UDP-glucose for the cytosolic enzyme Withania somnifera
2.4.1.173 0.024
-
 24-methylene cholesterol for the cytosolic enzyme Withania somnifera
2.4.1.173 0.119
-
 dehydroepiandrosterone for the cytosolic enzyme Withania somnifera
2.4.1.173 0.125
-
 stigmasterol for the cytosolic enzyme Withania somnifera

Metals/Ions

EC Number Metals/Ions Comment Organism Structure
2.4.1.173 additional information Mg2+, Mn2+, Ca2+, Co2+ do not show any effect Withania somnifera

Molecular Weight [Da]

EC Number Molecular Weight [Da] Molecular Weight Maximum [Da] Comment Organism
2.4.1.173 37000
-
 SDS-PAGE Withania somnifera

Organism

EC Number Organism UniProt Comment Textmining
2.4.1.173 Withania somnifera
-
-
-

Purification (Commentary)

EC Number Purification (Comment) Organism
2.4.1.173 Cibacron Blue column, Sephadex G-25 column and Mono Q anion exchange column Withania somnifera

Source Tissue

EC Number Source Tissue Comment Organism Textmining
2.4.1.173 leaf
-
 Withania somnifera
-

Specific Activity [micromol/min/mg]

EC Number Specific Activity Minimum [µmol/min/mg] Specific Activity Maximum [µmol/min/mg] Comment Organism
2.4.1.173 additional information
-
 the cytosolic enzyme shows 100% activity with 24-methylene chloseterol as substrate. Using Dehydroepiandrosterone, Stigmasterol, Brassicasterol, beta-sitosterol or Deacetyl-16-DPA the activtity is 75% - 44%. Using Diosgenin, Solasdine or Pregnenolene the activity is 31,5% - 14.1%. Using Cholesterol, 20S,22R-1alpha, 3beta-dihydroxy-witha-5,24-dienolide, Hecogenin, Tigogenin, Quercetin or Daidzein the activity is 8.9% - 2.1%. There is no activity, when using Euphol, Ursolic acid, Testosterone, Estradiol or Single glucose withanolide as substrate. Sterol glucosyltransferase activity is monitored radiometricaly using UDP-[U-14C] glucose as the radioactive substrate in the radioactive substrate Withania somnifera
2.4.1.173 additional information
-
 the membrane bound enzyme shows 100% activity with 24-methylene chloseterol as substrate. Using Deacetyl-16-DPA, beta-sitosterol, Brassicasterol, Dehydroepiandrosterone, Pregnenolene, Stigmasterol or Cholesterol the activtity is 577% - 124%. The enzyme shows 2% activity with Diosgenin as substrate. It does not show any activity with Solasodine 16,17alpha-epoxy prednenolene, Hecogenin, 20S,22R-1alpha, 3beta-dihydroxy-witha-5,24-dienolide, Tigogenin, Quercetin, Daidzein, Euphol, Ursolic acid, Testosterone, Estradiol or Single glucose withanolide. Withania somnifera

Substrates and Products (Substrate)

EC Number Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
2.4.1.173 24-methylene cholesterol + UDP-glucose
-
 Withania somnifera UDP + 24-methylene-cholesterol 3-beta-D-glucoside
-
 ?
2.4.1.173 3beta-hydroxy-pregna-5,16-dien-20-one + UDP-glucose
-
 Withania somnifera UDP + 3beta-20-oxopregna-5,16-dien-3-yl beta-D-glucopyranoside
-
 ?
2.4.1.173 beta-sitosterol + UDP-glucose
-
 Withania somnifera UDP + beta-sitosterol 3-beta-D-glucoside
-
 ?
2.4.1.173 dehydroepiandrosterone + UDP-glucose
-
 Withania somnifera UDP + dehydroepiandrosterone 3-beta-D-glucoside
-
 ?
2.4.1.173 diosgenin + UDP-glucose
-
 Withania somnifera UDP + diosgenin 3-beta-D-glucoside
-
 ?
2.4.1.173 additional information the enzyme is highly specific to sterols and shows no activity with non steroidal substrates. Amongst the sterols, the enzyme is position specific and works only with C-3 hydroxyl sterols, but the extradiol C-3 hydroxyl group is not glucosylated. Sterols with A-B ring 5-en (e.g. deacetyl-16-DPA) are glucosylated more efficiently than those with 5alpha-H. For the cytosolic enzyme, the relative substrate specificity of the membrane-bound enzyme is different. The membrane enzyme is more specific towards phytosterols and brassicasterol. It shows no activity towards secondary metabolits and flavonoids and isoflavonoids. Withania somnifera ?
-
 ?
2.4.1.173 pregnenolone + UDP-glucose
-
 Withania somnifera UDP + pregnenolone 3-beta-D-glucoside
-
 ?
2.4.1.173 stigmasterol + UDP-glucose
-
 Withania somnifera UDP + stigmasterol 3-beta-D-glucoside
-
 ?

Temperature Optimum [°C]

EC Number Temperature Optimum [°C] Temperature Optimum Maximum [°C] Comment Organism
2.4.1.173 30
-
-
 Withania somnifera

Turnover Number [1/s]

EC Number Turnover Number Minimum [1/s] Turnover Number Maximum [1/s] Substrate Comment Organism Structure
2.4.1.173 0.0023
-
 diosgenin for the cytosolic enzyme Withania somnifera
2.4.1.173 0.0037
-
 beta-sitosterol for the cytosolic enzyme Withania somnifera
2.4.1.173 0.0047
-
 pregnenolone for the cytosolic enzyme Withania somnifera
2.4.1.173 0.0072
-
 dehydroepiandrosterone for the cytosolic enzyme Withania somnifera
2.4.1.173 0.0087
-
 UDP-glucose for the cytosolic enzyme Withania somnifera
2.4.1.173 0.0088
-
 stigmasterol for the cytosolic enzyme Withania somnifera
2.4.1.173 0.0093
-
 3-beta-hydroxy-pregna-5,16-dien-20-one for the cytosolic enzyme Withania somnifera
2.4.1.173 0.38
-
 24-methylene cholesterol for the cytosolic enzyme Withania somnifera

pH Optimum

EC Number pH Optimum Minimum pH Optimum Maximum Comment Organism
2.4.1.173 8
-
-
 Withania somnifera

pH Range

EC Number pH Minimum pH Maximum Comment Organism
2.4.1.173 7 9 the enzyme has an optimum pH for activity around 8.0 with half maximal activities at 7.0 and above 9.0 Withania somnifera

pI Value

EC Number Organism Comment pI Value Maximum pI Value
2.4.1.173 Withania somnifera determined by chromatofocusing
-
 3.8

IC50 Value

EC Number IC50 Value IC50 Value Maximum Comment Organism Inhibitor Structure
2.4.1.173 0.04
-
 strongly inhibits the sterol glucosyltransferase activity, IC50 (mM): 0.04 Withania somnifera Zn2+
2.4.1.173 0.5
-
 strongly inhibits the sterol glucosyltransferase activity, IC50 (mM): 0.5 Withania somnifera Hg2+
2.4.1.173 1.2
-
 strongly inhibits the sterol glucosyltransferase activity, IC50 (mM): 1.2 Withania somnifera Ni2+
2.4.1.173 1.3
-
 strongly inhibits the sterol glucosyltransferase activity, IC50 (mM): 1.3 Withania somnifera Co2+