Properties of alpha-hydroxynitrile lyase from the petiole of cassava (Manihot esculenta Crantz).
alpha-Hydroxynitrile lyase (HNL, acetone-cyanohydrin lyase, EC 4.1.2.37) was purified to homogeneity from petioles of cassava (Manihot esculenta Crantz). The purified HNL is a homotetramer with a subunit molecular weight of 25,600 and an isoelectric point of 4.7. The HNL activity exhibits a pH optimum of 5.0 and is stable in the pH range of 6 to 11. The petiole HNL shows a simple Michaelis-Menten kinetics with Km for acetone cyanohydrin of 4.0 +/- 0.9 mM and Vmax of 46.2 +/- 5.0 micromol/min/mg. Several alcohols, aldehydes, and ketones inhibit the HNL activity. The alcohols and ketones are competitive inhibitors, whereas the aldehydes are noncompetitive inhibitors. On the basis of Ki values, inhibitors with 4 carbons are more potent than those with the same functional groups but having fewer or more than 4 carbons.
Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok, Thailand.
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Chueskul
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Chulavatnatol
D000438:Alcohols / Q000494:pharmacology; D000446:Aldehyde-Lyases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D000447:Aldehydes / Q000494:pharmacology; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D046911:Macromolecular Substances; D002365:Manihot / Q000201:enzymology*; D008970:Molecular Weight; D018515:Plant Leaves; D013379:Substrate Specificity
D000438:Alcohols; D000447:Aldehydes; D046911:Macromolecular Substances; D000446:Aldehyde-Lyases; C087495:acetone-cyanohydrin lyase