Rhizobia utilize phenolic substances as sole carbonsource. Bradyrhizobium japonicum utilizescatechin, a unit of condensed tannin as carbonsource. To establish the degradative pathway ofcatechin, the products of catechin degradation wereisolated by paper chromatography and TLC andidentified by HPLC, UV, IR and NMR spectra. B.japonicum cleaves catechin through catechinoxygenase. Phloroglucinolcarboxylic acid andprotocatechuic acid were identified as the initialproducts of degradation. Phloroglucinolcarboxylicacid is further decarboxylated to phloroglucinolwhich is dehydroxylated to resorcinol. Resorcinolis hydroxylated to hydroxyquinol. Protocatechuicacid and hydroxyquinol undergo intradiol cleavagethrough protocatechuate 3,4-dioxygenase andhydroxyquinol 1,2-dioxygenase to formβ-carboxy cis, cis-muconic acidand maleylacetate respectively. The enzymes ofcatechin degradative pathway are inducible. Estimation of all the enzymes involved in thecatabolism of catechin reveals the existence of acatechin degradative pathway in B. japonicum.

Degradation of catechin by Bradyrhizobium japonicum

Protocatechuic acid (I), homoprotocatechuic acid (II), and protocatechuic aldehyde (III) were sepd. by paper chromatog. on Whatman no. 1 filter paper and then detected with a new reagent contg. $FeCl_3$ and $NH_4$ molybdate. Six solvent systems were tested, and the best results were obtained with 2% $HCOOH$. On the chromatograms, I and III gave bluish green spots, and II gave a dark brown spot. This new $FeCl_3-NH_4$ molybdate reagent was also used successfully for detn. of I by photometry. The absorbance was linearly related to 10-100 \mug

Separation of protocatechuate and homoprotocatechuate by paper chromatography and estimation of protocatechuate by colorimetry using a new $FeCl_3$ reagent

Ganapathi S Raju

Papers

Separation of protocatechuate and homoprotocatechuate by paper chromatography and estimation of protocatechuate by colorimetry using a new $FeCl_3$ reagent