Diphenol Activation of the Monophenolase and Diphenolase Activities of Field Bean (Dolichos lablab) Polyphenol Oxidase

2002 ◽  
Vol 50 (6) ◽  
pp. 1608-1614 ◽  
Author(s):  
Lalitha R. Gowda ◽  
Beena Paul
Keyword(s):  
Polyphenol Oxidase ◽  
Field Bean ◽  
Dolichos Lablab

The unique enzymatic function of field bean (Dolichos lablab) d-galactose specific lectin: a polyphenol oxidase

2008 ◽  
Vol 26 (5) ◽  
pp. 535-545 ◽  
Author(s):  
Santosh R. Kanade ◽  
Devavratha H. Rao ◽  
Ramanath N. Hegde ◽  
Lalitha R. Gowda
Keyword(s):  
Polyphenol Oxidase ◽  
Field Bean ◽  
Dolichos Lablab ◽  
Enzymatic Function

scholarly journals The conformational state of polyphenol oxidase from field bean (Dolichos lablab) upon SDS and acid-pH activation

2006 ◽  
Vol 395 (3) ◽  
pp. 551-562 ◽  
Author(s):  
Santosh R. Kanade ◽  
Beena Paul ◽  
A. G. Appu Rao ◽  
Lalitha R. Gowda
Keyword(s):  
Polyphenol Oxidase ◽  
Insect Herbivory ◽  
Catalytic Efficiency ◽  
Critical Micellar Concentration ◽  
Field Bean ◽  
Ph Optimum ◽  
Dolichos Lablab ◽  
Acid Ph ◽  
Stokes Radius ◽  
Increased Sensitivity

Field bean (Dolichos lablab) contains a single isoform of PPO (polyphenol oxidase) – a type III copper protein that catalyses the o-hydroxylation of monophenols and oxidation of o-diphenols using molecular oxygen – and is a homotetramer with a molecular mass of 120 kDa. The enzyme is activated manyfold either in the presence of the anionic detergent SDS below its critical micellar concentration or on exposure to acid-pH. The enhancement of kcat upon activation is accompanied by a marked shift in the pH optimum for the oxidation of t-butyl catechol from 4.5 to 6.0, an increased sensitivity to tropolone, altered susceptibility to proteolytic degradation and decreased thermostability. The Stokes radius of the native enzyme is found to increase from 49.1±2 to 75.9±0.6 Å (1 Å=0.1 nm). The activation by SDS and acid-pH results in a localized conformational change that is anchored around the catalytic site of PPO that alters the microenvironment of an essential glutamic residue. Chemical modification of field bean and sweet potato PPO with 1-ethyl-3-(3-dimethylaminopropyl)carbodi-imide followed by kinetic analysis leads to the conclusion that both the enzymes possess a core carboxylate essential to activity. This enhanced catalytic efficiency of PPO, considered as an inducible defence oxidative enzyme, is vital to the physiological defence strategy adapted by plants to insect herbivory and pathogen attack.

The enzymatic lectin of field bean (Dolichos lablab): Salt assisted lectin–sugar interaction

2012 ◽  
Vol 83 ◽  
pp. 7-14 ◽  
Author(s):  
Devavratha H. Rao ◽  
Yashavanth L. Vishweshwaraiah ◽  
Lalitha R. Gowda
Keyword(s):  
Field Bean ◽  
Dolichos Lablab
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