ISSN:
1399-3054
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
The mechanism for uptake of glycolate in the cyanobacterium Anabaena 7120 and its capacity to metabolize glycolate were examined. The uptake of [14C]-glycolate in light, at pH 7, consisted of an initial rapid phase (≤60s) 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 ΔΨ only slightly reduced the uptake of glycolate. At pH 7.0, the F0F1-ATPase inhibitor N, N′-dicyclohexylcarbodiimide (DCCD) and the uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP) abolished the uptake. Inhibition of photophosphorylation by dark-treatment and presence of 3-(3′,4′-dichlorophenyl)-1, 1-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 ΔpH 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 μmol (mg chl a)−1 h−1 in young cultures. In older cultures the rate was nearly 50% lower.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1399-3054.1989.tb06161.x
Permalink
