• 한국미생물·생명공학회지
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• 제19권2호
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• pp.128-134
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• 1991

To study the reduced growth and synthesis, proeviously reported, of ${\beta}$-galactosidase of alkalophilic Bacillus sp. YS-309 at the higher lactose concentration of 0.5% (w/v) in the medium, lactose transport and utilization were examined. The results showed that lactose transport was influenced by the addition of four kinds of antibiotics, and tetracycline stimulated most but not valinomycin. PEP-potentials of the cells grown on lactose was estimated lower than the cells on glucose and on galactose. Thus, the transport of lactose was independent of intracellular PEP and phosphorylation reactions, and was thought to be uptaked directly or oxidized in part in the transport process. In the other hand, once lactose was uptaked into the cells, it was hydrolyzed by ${\beta}$-glactosidase to glucose and galactose. The former was metabolized fast but the latter was accumulated. Galactose and lactose were not utilized until glucose was mostly depleted in the medium. The ${\beta}$-galactosidase synthesis decreased in the presence of glucose over 0.2% and galactose over 0.05 to 0.1%, respectively. In conclusion, it was considered for glucose as a repressor and galactose as a inducer for ${\beta}$-galactosidase synthesis even though the mechanisms were not elucidated. Catabolite repression of glucose on the enzyme synthesis was not relieved by the addition of exogeneous cAMP.

• 미생물학회지
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• 제27권3호
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• pp.181-187
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• 1989

Lactobacillus casei SW-M1으로부터 lactose 이용 pPLac Plasmid를 분리하였다. 이 plasmid에 lactose이용 유전자가 존재하는지를 확이하기 위하여 plasmid curing을 실시한 결과, acriflavin 8mg/ml 과 11 mg/ml EtBr를 처리한 후 , 3차 접종 배양의 경우에 curing 빈도가 가장 높았다. Lac와 plasmid가 cured 된 $Lac^{+}$strain의 당 이용능을 조사한 결고, glucose lactosidasedldydsmd은 불변이나, lactosedldydsmd만이 $Lac^{+}$strain에서 감소하였다 pPLac plasmid의 lactose 분해능은 $\beta$-galactosidase 에 의한 것이 아니고, phospho-$\beta$-galactosidase 에 의한 것으로 확인되었다. $Lac^{+}$strain의 carbohydrate가 막투과시 PTS과 관련이 있는가를 조사한 결과ㅏ lactose-PTS가 가장 활성이 높았으며, 그 다음이 galactose-PTS, glucose-PTS 로 나타났다. 그러므로 lactose는 lactose-PTS(lactose-phosphotransferase system)에 의하여 glucose와 galactose-6-phosphate로 분해됨을 알 수 있었다. Phospho-$\beta$-galactosidase의 induction 실험에서는 galactoserk 가장 높은 induction 효과를 보여 주었으며, lactose와 glucose는 높은 수준의 induction을 나타내었으며, IPTG는 induction 효과가 없었다. Glucosedh lactose 배지에서 L. casie는 diauxic growth나 phospho-$\beta$-galactosidase합성을 조사한 결과, catabolite repression을 받지 않는 것으로 나타났다.

• Reproductive and Developmental Biology
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• 제39권4호
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• pp.97-104
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• 2015

Glucose is universal and essential fuel of energy metabolism and in the synthesis pathways of all mammalian cells. Glucose is the one of the major precursors of lactose synthesis using glycolysis result in producing milk fat and protein. During the milk fat synthesis, lipoprotein lipase (LPL) and CD36 are required for glucose uptake. Various morecules such as acyl-CoA synthetase 1 (ACSL1) activity of acetyl-CoA synthetase 2 (ACSS2), ACACA, FASN AGPAT6, GPAM, LPIN1 are closely related with milk fat synthesis. Additionally, glucose plays a major role for synthesizing lactose. Activations of lactose synthesize enzymes such as membranebound enzyme, beta-1,4-galactosyl transferase (B4GALT), glucose-6-phosphate dehydrogenase (G6PD) are changed by concentration of glucose in blood resulting change of amount of lactose production. Glucose transporters are a wide group of membrane proteins that facilitate the transport of glucose over a plasma membrane. There are 2 types of glucose transporters which consisted facilitative glucose transporters (GLUT); and sodium-dependent transport, mediated by the Na+/glucose cotransporters (SGLT). Among them, GLUT1, GLUT8, GLUT12, SGLT1, SGLT2 are main glucose transporters which involved in mammary gland development and milk synthesis. However, more studies are required for revealing clear mechanism and function of other unknown genes and transporters. Therefore, understanding of the mechanisms of glucose usage and its regulation in mammary gland is very essential for enhancing the glucose utilization in the mammary gland and improving dairy productivity and efficiency.