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ISSN 0582-9879 Acta Biochim et Biophysica Sinica 2004, 36(4):290-296 CN 31-1300/Q
The Recognition
of Glycolate Oxidase Apoprotein with Flavin Analogs in Higher Plants
Wei-Jun WANG*, Jing-Quan
HUANG, Chong YANG, Jiu-Jiu HUANG, and Ming-Qi LI
( College of Life Science, South China Agricultural University, Guangzhou 510642,
China )
Abstract The dependence of
glycolate oxidase apoprotein (apoGO) activity on flavin analogs was surveyed
in 9 higher plants from 7 families. Activities of all apoGOs depended not only
on flavin mononucleotide (FMN) but also on flavin adenine dinucleotide (FAD),
but not on riboflavin. The kinetic analysis
showed that FMN was the optimum cofactor for apoGO from leaves of Brassica
campestris. In plant kingdom, FMN, FAD and riboflavin are three flavin analogs
with very similar structure, and they could coexist and be inter-converted from
each other, so the question is how the apoprotein of glycolate oxidase (GO)
recognized these flavin analogs. No inhibition effect of riboflavin on the activity
of apoGO with FMN or FAD was found and no obvious quenching of riboflavin or
apoGO protein fluorescence was detected with the addition of apoGO or riboflavin,
respectively. These results indicated that riboflavin did not bind to apoGO
tightly like FMN and FAD. Inorganic phosphate (Pi) did inhibit the activity
of GO, and kinetic analysis revealed that this inhibition was caused by the
competitive binding to apoGO between Pi and FMN. This competitive binding was
further confirmed by the inhibition of Pi to the quenching of FMN and apoGO
protein fluorescence with apoGO and FMN, respectively. It was suggested that
the 5′-phosphate group of FMN or FAD may play a key role in the recognition
and binding of riboflavin analog cofactors with apoGO.
Key words glycolate oxidase
in higher plant; flavin analogs; 5′-phosphate moiety; recognition
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Received: November 26, 2003 Accepted:
January 15, 2004
This work was supported by the grants from the National Natural Science Foundation
of China (No. 39900008) and Natural Science Foundation of Guangdong Province
(No. 990693)
*Corresponding author: Tel, 86-20-85287058; Fax, 86-20-85287058; E-mail, [email protected]