The enzyme catalyzing the transfer of glucose from uridine diphosphate glucose to indoxyl yielding the indoxyl glucoside indican was isolated from Baphicacanthus cusia Bremek (Acanthaceae). The indoxyl-uridine diphosphate glucose (UDPG)-glucosyltransferase was purified to homogeneity in six chromatographic steps. The decisive step for the recovery of a homogeneous enzyme was the application of immobilized metal affinity chromatography yielding an 863-fold purified enzyme. From a total of 60 substances tested, in addition to the natural substrate 3-OH-indole (indoxyl), only 4-OH-, 5-OH-, 6-OH-, and 7-OH-indole were accepted as substrates by the glucosyltransferase. However, the latter substrates were metabolized to varying extent. The optimum pH of the enzyme was 8.5, the optimum temperature was 30°C and the isoelectric point was pH 6.5. The Mr of the enzyme was determined to be 60 ± 2 × 10^3. Indoxyl as substrate yielded a Km of 1.2 mM, while a Km of 1.7 mM was found for UDPG.

Baphicacanthus cusia; Acanthaceae; indoxyl-UDPG-glucosyltransferase; enzyme purification; enzyme characterization

• Compound ID: 32288
  

  b-D-Glcp-(1-3)-Subst Subst = 1H-indol-3-ol = SMILES O{3}C1={1}CNC2=CC=CC=C21

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  Structure type: monomer
  Trivial name: indican
  Compound class: glycoside
  
   
  
  Baphicacanthus cusia
  CSDB ID 66723 (all data & tools)