Improvement of polyhydroxybutyrate production by deletion of csrA in Escherichia coli

BACKGROUND: Poly-3-hydroxybutyrate (PHB) can be efficiently produced in recombinant Escherichia coli by the overexpression of an operon (NphaCAB) encoding PHB synthetase. Strain improvement is considered to be one of critical factors to lower the production cost of PHB in recombinant system. In this study, one of key regulators that affect the cell growth and PHB content was confirmed and analyzed. RESULT: S17-3, a mutant E. coli strain derived from S17-1, was found to be able to achieve high cell density when expressing NphaCAB with the plasmid pBhya-CAB. Whole genome sequencing of S17-3 revealed genetic alternations on the upstream regions of csrA, encoding a global regulator cross-talking between stress response, catabolite repression and other metabolic activities. Deletion of csrA or expression of mutant csrA resulted in improved cell density and PHB content. CONCLUSION: The impact of gene deletion of csrA was determined, dysfunction of the regulators improved the cell density of recombinant E. coli and PHB production, however, the detail mechanism needs to be further clarified.

Importancia del metabolismo de la biotina / Importance of biotin metabolism

La biotina pertenece al grupo de las vitaminas hidrosolubles del complejo B. En humanos la biotina está directamente involucrada en importantes procesos metabólicos como la gluconeogénesis, la síntesis de ácidos grasos y el catabolismo de algunos aminoácidos, debido a su papel como grupo prostético de las enzimas piruvato carboxilasa, propionil-CoA carboxilasa, b-metilcrotonil-CoA carboxilasa y de la acetil-CoA carboxilasa. La biotina se une al sitio activo de estas enzimas y funciona como acarreador de CO2. Las carboxilasas se sintetizan como apocarboxilasas, carentes de biotina y la forma activa se produce por la unión covalente de la biotina al grupo e-amino de un residuo de lisina de la apocarboxilasa, reacción catalizada por la holocarboxilasa sintetasa. El paso final de la degradación de las carboxilasas es el rompimiento de la fracción biotinil del grupo e-amino de la lisina que es catalizada por la biotinidasa y resulta en la liberación de la biotina libre, la cual puede ser nuevamente reciclada. La biotina regula, a nivel postranscripcional, la expresión de la propionil-CoA carboxilasa y, a nivel transcripcional, a la de la holocarboxilasa sintetasa. Además de su papel como cofactor y regulador de la biosíntesis de las carboxilasas, la biotina está involucrada en otras áreas del metabolismo, donde regula la síntesis de proteínas específicas entre las que se encuentran el receptor de la asialoglicoproteína, varias enzimas reguladoras del metabolismo de glucosa y proteínas que unen biotina en la yema de huevo, entre otras. La deficiencia de biotina se ha reportado en pacientes sometidos a una alimentación parenteral total, en personas que ingieren grandes cantidades de clara de huevo crudo, en niños con desnutrición energético proteínica severa y en personas con errores innatos del metabolismo. Entre estas últimas se encuentran las enfermedades autosómicas recesivas del metabolismo de biotina que resultan de la alteración de la actividad de la holocarboxilasa sintetasa o de la biotinidasa.

Control of Na+ channels in salivary duct cells

No abstract available.

Regulation of acetyl CoA carboxylase mRNA in rat liver by high carbohydrate diet and insulin

Acetyl CoA carboxylase contents in liver cytosol of rats refed a high carbohydrate diet or injected with insulin were measured by an immunoassay method in order to evaluate the effects of dietary carbohydrate and insulin treatment on the control in the amount of acetyl CoA carboxylase. Acetyl CoA carboxylase was purified 1,552 folds with a specific activity of 3.88 units/mg protein from livers of rats refed a high carbohydrate diet for 3 days following a 3-day fasting and the antibody was generated against the purified acetyl CoA carboxylase in a rabbit. Treatment of insulin (1.5 units/100g BW) and a high carbohydrate diet increased the amount of acetyl CoA carboxylase in liver cytosol by 3 times and 10 times, respectively, when compared to the enzyme content found in the control. The synthetic ratio of acetyl CoA carboxylase to total cytosolic proteins was 4 times higher in the insulin-treated group and 10 times higher in the high carbohydrated diet-treated group than the control group. The polysomal RNA contents in liver cytosols were 279% of the control in the insulin-treated group and 365% of the control in the high carbohydrate diet group. Also, the nascent chain of acetyl CoA carboxylase in polysome were 158% of the control in the insulin-treated group and 311% of the control in the high carbohydrate treated group. From these results, it is assumed that the increase of acetyl CoA carboxylase content in the rat liver cells by insulin treatment, or high carbohydrate diet refeeding has resulted from the increased polysomal acetyl CoA carboxylase mRNA, which is directly related to the biosynthesis of this enzyme.

Regulation of acetyl CoA carboxylase mRNA in rat liver by high carbohydrate diet and insulin

Acetyl CoA carboxylase contents in liver cytosol of rats refed a high carbohydrate diet or injected with insulin were measured by an immunoassay method in order to evaluate the effects of dietary carbohydrate and insulin treatment on the control in the amount of acetyl CoA carboxylase. Acetyl CoA carboxylase was purified 1,552 folds with a specific activity of 3.88 units/mg protein from livers of rats refed a high carbohydrate diet for 3 days following a 3-day fasting and the antibody was generated against the purified acetyl CoA carboxylase in a rabbit. Treatment of insulin (1.5 units/100g BW) and a high carbohydrate diet increased the amount of acetyl CoA carboxylase in liver cytosol by 3 times and 10 times, respectively, when compared to the enzyme content found in the control. The synthetic ratio of acetyl CoA carboxylase to total cytosolic proteins was 4 times higher in the insulin-treated group and 10 times higher in the high carbohydrated diet-treated group than the control group. The polysomal RNA contents in liver cytosols were 279% of the control in the insulin-treated group and 365% of the control in the high carbohydrate diet group. Also, the nascent chain of acetyl CoA carboxylase in polysome were 158% of the control in the insulin-treated group and 311% of the control in the high carbohydrate treated group. From these results, it is assumed that the increase of acetyl CoA carboxylase content in the rat liver cells by insulin treatment, or high carbohydrate diet refeeding has resulted from the increased polysomal acetyl CoA carboxylase mRNA, which is directly related to the biosynthesis of this enzyme.