3-hydroxybutyrate Production Research Articles

Enhancement of growth and poly 3-hydroxybutyrate production from Methylobacterium sp. ZP24 by formate and other organic acids

Production of the polymer, poly 3-hydroxybutyrate (PHB), by Methylobacterium sp. ZP24 increased when sucrose-containing medium was partially substituted with low concentrations of several organic acids. Low concentrations of formate could enhance the PHB yield 2·4-fold and bring down the production time by 12 h. The use of formate as a growth enhancer could be successfully scaled up to the 18 litre level. The possible mechanism of enhancement is discussed.

The effects of insulin and glucagon on ketone-body turnover.

A double-isotope procedure was used to measure the effects of insulin and glucagon on ketone-body production and utilization (i.e. turnover) in the starved rat. Somatostatin was infused during the experiment to suppress the pancreatic release of either hormone. The immediate action of insulin in terms of ketone-body turnover that was most evident was a decreased production of 3-hydroxybutyrate, with no significant change in the turnover of acetoacetate. Similarly, the significant effect of glucagon infusion was to increase the production of 3-hydroxybutyrate, with minimum increase in acetoacetate turnover. The data support a direct effect of both hormones on the distribution of acetyl units derived from fatty acid beta-oxidation.

A double-isotope method for the measurement of ketone-body turnover in the rat. Effect of L-alanine.

The synthesis of 4-3H-labelled ketone bodies, and their use along with 14C-labelled ketone-body precursors, is employed using an 'in vivo' rat infusion model to measure ketone-body turnover. The use of two isotopes is necessary to measure ketone-body turnover when ketogenesis may occur from more than one precursor such as glucose and fatty or amino acids. Requirements of isotopic equivalence in terms of metabolic similarity, valid stoichiometry and the lack of differences in the kinetics of relevant enzymes is demonstrated for the 4-3H- and 14C-labelled ketone bodies. The hypoketonaemic effect of L-alanine is shown by two distinct phases after the administration of L-alanine. During the first 12 min after alanine administration ther was a 50% decrease in acetoacetate and a 30% decrease in 3-hydroxybutyrate production, with no significant change in the utilization of either compound. The hypoketonaemic action of alanine during the following 16 min was primarily associated with an uptake of 3-hydroxybutyrate that was somewhat greater than the increase in its production. There were essentially equivalent decreases in production and utilization of acetoacetate, resulting in no significant net change in the level of this ketone body in the blood.

3-hydroxybutyrate dehydrogenase in tissues from normal and ketonaemic sheep.

1. In liver, rumen epithelium and kidney cortex of the sheep, a dehydrogenase active against dl-3-hydroxybutyrate occurred in both the cytosol and particulate fractions of the tissues. In brain, heart, skeletal and smooth muscles, the enzyme occurred only in the particulate fraction. 2. Enzyme activity in the cytoplasmic fraction of liver and rumen epithelium was similar with either d(-)-3-hydroxybutyrate or dl-3-hydroxbutyrate, but was less with acetoacetate as the substrate. The cytosol fraction of kidney cortex showed very little activity with d(-)-3-hydroxybutyrate, confirming that most of the activity with dl-3-hydroxybutyrate was with the l(+) isomer in this tissue. 3. 3-Hydroxybutyrate dehydrogenase activities in the cytosol and particulate fractions of liver, rumen epithelium and kidney cortex and in the particulate fraction of brain tissue were not stimulated by phosphatidylcholine, unlike the enzyme in sheep muscle and in tissues of other species. 4. The activity of 3-hydroxybutyrate dehydrogenase was not increased significantly in any of the tissues of ketonaemic sheep. 5. Comparison of rates of 3-hydroxybutyrate production in vivo with the enzyme activity in ketogenic tissue suggested that in sheep the maximum rate of production might be limited by this activity.