The metabolism of carbohydrates by extremely halophilic bacteria: identification of galactonic acid as a product of galactose metabolism

Abstract

Cell-free extracts prepared from the extremely halophilic bacterium Halobacterium saccharovorum oxidize galactose and accumulate a product which reacts as if it were a lactone. The product does not act as a reducing sugar and contains all six of the carbon atoms initially present in galactose. The product was jugged to be galactonic acid, based on the behavior of the acetylmethyl ester derivative of the product and the pentaacetyl derivative of the galactonic methyl ester during gas chromatography.

A plasma global metabolic profiling approach applied to an exercise study monitoring the effects of glucose, galactose and fructose drinks during post-exercise recovery

“…3). Galactonic acid has previously been identified as a product of galactose metabolism within humans [41,42] Bergren et al managed to isolate galactonic acid in the urine of galactosemia patients after being given an oral dose of galactose, the results from this work indicated that there is an oxidative pathway for the metabolism of galactose in human subjects, however they did not measure galactonic acid levels in blood. Observation of high levels of fructose and galactonic acid from galactose metabolism described above in blood via the metabolomic approach does suggest that not all the ingested fructose and galactose was metabolized within the liver.…”

The Halobacteriaceae

“…More recently, a number of isolates have been found that grow well on individual sugars as single carbon sources. Hochstein's group (Tomlinson et al, 1974;Hochstein et al, 1976;Hochstein, 1978) isolated a number of halobacteria that produced sugars from carbohydrates. Halobacterium saccharovorum, the species most studied, metabolizes glucose by a modified Entner-Doudoroff pathway and can produce galactonic acid from galactose and lactobionic acid from lactose.…”

Glucose metabolism in the extreme thermoacidophilic archaebacterium Sulfolobus solfataricus

“…Gluconic acid was identified as the penta-acetyl methyl ester derivative by g.l.c. by using the procedure of Hochstein et al (1976); pyruvic acid and glyceraldehyde were identified enzymically by NADH oxidation in the presence of lactate dehydrogenase and alcohol dehydrogenase respectively, and spectroscopically by 1H n.m.r. The 2keto-3-deoxygluconic acid obtained by chemical synthesis and that produced by enzymic degradation of glucose were compared by 1H-n.m.r.…”