Glycolate metabolism in cyanobacteria

Abstract

1989. Glycolate metabolism in cyanobacteria. 11. Evidence for a mediated transport of glycolate in Anabaena 7120. -Physiol. Plant. 75;[144][145][146][147][148][149][150] The mechanism for uptake of glycolate in the cyanobacterium Anabaena 7120 and its capacity to metabolize glycolate were examined. The uptake of ['^C]-glycolate in light, at pH 7, consisted of^ an initial rapid phase (<60 s) and a second slower phase. The latter obviously represents metabolism as the glycolate dehydrogenase inhibitor 2-pyridylhydroxymethanesulfonic acid (HPMS) did not affect the initial uptake phase while the second phase was strongly reduced. The sulfhydryl reagent N-ethylmaleimide (NEM) inhibited uptake of glycolate and the uptake was reduced by lactate, glycerate and glyoxylate. Treatment with triphenylmethylphosphonium (TPMP^), a lipophilic cation collapsing A\p only slightly reduced the uptake of glycolate. At pH 7.0, the F,,F,-ATPase inhibitor N,N'-dieyclohexylcarbodiimide (DCCD) and the uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP) abolished the uptake. Inhibition of photophosphorylation by dark-treatment and presence of 3-(3',4'-dichlorophenyl)-l,l-dimethylurea (DCMU) also reduced the uptake. Decreasing the pH in the range of 10 to 5.5 increased the uptake. In contrast to the situation at pH 7, CCCP did not affect the initial glycolate uptake at pH 5.5. We conclude that the uptake of glycolate is a carrier-mediated process which, at pH 7, is dependent on a H^-ATPase to create the ApH across the membranes needed for uptake, while at pH 5.5 the uptake of glycolate is not ATP-dependent. The capacity to metabolize glycolate was at least 50 (xmol (mg chl a)"' h"' in young cultures. In older cultures the rate was nearly 50% lower.

The transport of glycolic acid by Chlamydomonas reinhardtii

“…3). As with Anabeana [3] 10 mM NEM inhibited the uptake of glycolate in Chlarnydomonas (Fig, 3) but inhibition was not as great as in erythrocytes.…”

“…Decreased glycolate uptake by competition with structural analogs such as acetate, lactate and glycerat¢ was not observed, The difference between Anabeana [3] and Chlamydomonas in regard to inhibition by substrate analogs may be partly due to differences m experimental design and the rapid equilibrium in Chlamydomonas. Studies of uptake of glycolic acid by Chlamydomonas in contrast to the chloroplasts and Anabeana may be complicated by transport across organelle membranes as well as across the plasma membrane.…”

“…Howitz and McCarty [1,2] have described a giycolate transporter in chloroplasts and Renstrom eta[. [3] have described a glyeolate transporter in Anabeana.…”

Glycolate metabolism in cyanobacteria

“…An efficient CO2-concentrating mechanism could explain the reduced phosphoglycolate production. However, in the accompanying paper (Renstrom et al 1989) we show that Anabaena 7120 takes up and metabolizes appreciable quantities of externally added glycolate. This indicates that the glycolate eventually produced in Anabaena 7120 may be retained and metabolized intracellularly.…”