MAL64 c is a global regulator of α-glucoside fermentation: identification of a new gene involved in melezitose fermentation

Summary Maltase constitutive mutants at the MAL6 locus have been mapped to the newly identified regulatory gene MAL64 ^c. We show here that MAL64 ^c has in addition pleiotropic effects on sugar fermentation: MAL64 ^c strains constitutively synthesize an -methylglucosidase and can complement a new gene, MTP1, for the fermentation of melezitose and -methylglucoside. MTP1, maps near MAL1, and either encodes a permease which transports melezitose, -methylglucoside, and maltose or regulates the activity of such a permease. This work shows that MAL64 ^c, a trans-acting regulatory gene, is a global regulatory gene affecting several different pathways of -glucoside metabolism.     

Further evidence for the alternative pathway of trehalose synthesis linked to maltose utilization in Saccharomyces

Summary Yeast strains bearing a deficiency in trehalose-6-phosphate synthase activity are unable to accumulate trehalose on any carbon source unless they contain one of the MAL genes. If the gene is inducible then synthesis of trehalose occurs specifically during growth on maltose when the MAL gene is constitutive then trehalose accumulation can also be seen when cells are grown on glucose. Different systems for trehalose synthesis were suggested: one of them would require the UDPG-linked trehalose synthase whereas the second would utilize an alternative pathway. We proposed a mechanism by which the gene-product of a MAL gene would serve as a common positive regulator for the expression of the genes coding for maltose permease, -glucosidase and some component of the trehalose accumulation system. In order to elucidate this novel pathway a strain lacking UDPG-linked trehalose synthase activity and harboring a defect in maltose uptake was constructed. Excessive maltose uptake resulted in accumulation of intracellular maltose, and twice as much trehalose as in a control strain. Partial inhibition of hexokinase by xylose affected the ratio between internal maltose and trehalose and significantly reduced glycogen synthesis. Sodium fluoride also blocked glycogen synthesis but allowed for trehalose accumulation. Moreover, a mutant which lacks hexokinase I and II was unable to accumulate trehalose when grown on glucose in spite of the presence of a constitutive MAL2 gene. These results suggest that trehalose synthesis would require G-6-P formation derived from maltose. Such a deviation would allow for slowing down the glycolytic flux which, in turn, would favour efficient maltose utilization. Therefore, trehalose synthesis during growth in media containing glucose serves as an additional parameter for assessing constitutivity of MAL genes.     

麦芽糖注射液对2型糖尿病糖脂代谢和胰岛素分泌影响的研究

目的探讨麦芽糖注射液对2型糖尿病血糖、脂质代谢及胰岛素分泌的影响,并评价其供能的有效性。方法59例2型糖尿病患者随机分为麦牙糖组和氯化钠组,分别静脉输注10%麦芽糖注射液或0.9%氯化钠注射液各500 ml。观察输注前后血糖(BG)、血C肽、血游离脂肪酸(FFA)、血酮体、尿糖及尿酮变化。结果①麦芽糖组(A组)用药后1、2、3、5h静脉血糖均较用药前有所增加,其增量分别为(0.04±0.82)mmol/L、(0.39±1.19)mmol/L、(0.50±1.37)mmol/L、(0.14±1.24)mmo1/L,氯化钠组(B组)则较用药前有所下降,其血糖下降值各为(0.93±1.05)mmol/L、(1.12±1.05)mmol/L、(1.28±1.05)mmol/L、(1.66±1.20)mmol/L,两组比较差异有统计学意义(P<0.01);②两组用药后5 h内血浆游离脂肪酸(FFA)及血酮体均有下降,但氯化钠组下降不如麦芽糖果组明显,两组比较差异有统计学意义;③麦芽糖组用药后C肽及尿糖水平有所增加,尿酮治疗前后变化两组差异无统计学意义(P>0.05)。结论麦芽糖注射液用于2型糖尿病患者,在提供能量时未引起血、尿酮体升高,还能降低血FFA浓度,虽然开始治疗5h内血糖水平有所提高,但其升值幅度不大,故在监测血糖情况下,使用是安全的。     

Dietary sugars and subclinical vascular damage in moderate-to-high cardiovascular risk adults

Background and aimsThe association between dietary sugars and vascular damage has been scarcely examined out of the context of established cardiovascular disease. We aimed to investigate the association between different types of sugars with subclinical atheromatosis and arteriosclerosis, in individuals free of cardiovascular disease being, however, at moderate-to-high cardiovascular risk.Methods and resultsTwo 24-h dietary recalls were conducted to estimate sugars intake. Subclinical atheromatosis was assessed by B-mode ultrasonography and arteriosclerosis (arterial stiffness) via tonometry (carotid-to-femoral pulse wave velocity). Multiple logistic regression analysis was performed to determine the relationship of quartiles of total sugars, monosaccharides and disaccharides with atheromatosis and arteriosclerosis, adjusting for potential confounders [Odds Ratio (95%Confidence Interval)]. In 901 participants (52.4 ± 13.8 years, 45.2% males), total sugars intake was not associated with any type of subclinical vascular damage. Subjects at 4th quartile of lactose intake (15.3 ± 5.5 g/day) had lower probability to present atheromatosis compared to those at 1st quartile (0.00 ± 0.01 g/day) even in the fully adjusted model [0.586 (0.353–0.974)]. Subjects at 3rd quartile of total disaccharides intake and particularly sucrose (15.1 ± 2.2 g/day) had higher probability to present arteriosclerosis compared to those at 1st quartile (3.0 ± 1.9 g/day) even after adjustment for all potential confounders [2.213 (1.110–4.409)].ConclusionsOverall, the present data suggest a distinct role of each type of sugars on vascular damage. These observations highlight the need for further studies investigating not only foods rich in sugars, but sugars as separate components of food as they probably contribute via different ways on the development of arterial pathologies.     

HPLC-ELSD一测多评法同时测定蜂蜜中4种糖类成分

目的：建立同时测定蜂蜜中果糖、葡萄糖、蔗糖、麦芽糖含量的高效液相色谱法。方法：采用高效液相色谱法,使用Prevail Carbohyrate ES色谱柱,乙腈-水（78∶22）为流动相,流速为1.0 mL·min-1,柱温30 ℃,检测器为蒸发光散射检测器,漂移管温度为105 ℃,氮气流速为3.0 mL·min-1,进样量为10 μL。以果糖为内参物,测定其与葡萄糖、蔗糖、麦芽糖的相对校正因子,利用该相对校正因子计算3种成分的含量,同时利用外标法测定3种糖类成分的含量,比较结果的差异。结果：果糖与葡萄糖、蔗糖、麦芽糖的相对校正因子分别为0.931、1.535、1.111,RSD均＜2%;成分含量计算值与实测值间无显著性差异。结论：建立的一测多评法可用于蜂蜜中4种糖类成分的含量测定,可为蜂蜜的质量控制提供科学的理论依据。     

The Suitability of Maltose for Parenteral Nutrion

Maltose infusion were performed in rats and normal human subjects. Utilisation of maltose in a rat is fairly good. Blood glucose and lactic acid concentrations are elevated during the high dose of maltose in the rat and renal loss is limited to less than 5 % of the total amount infused. In the human subject no steady state is reached during the 4 hour continuous infusion and the renal loss of maltose and glucose was 31 % of the intravenous load. In contrast to the rat the blood glucose concentration in man did not increase. The metabolic utilisation of maltose in man was however demonstrated by a decrease in inorganic phosphate and serum free fatty acid concentration. It is concluded that maltose is not suited as a fuel for parenteral nutrition because of its low metabolic rate in the human being.     

原癌基因LMO2短剪切模式的结合蛋白鉴定及功能分析

目的 研究原癌基因LMO2短剪切模式(LMO2-C)的结合蛋白在白血病细胞K562中的表达及功能分析.方法 利用麦芽糖结合蛋白(MBP)沉淀技术和哺乳动物双杂交技术研究LMO2-C的结合蛋白在K562细胞中的表达;半定量RT-PCR检测过表达LMO2-C的K562细胞中红系发育的标志性基因GPA的表达水平.结果MBP原核表达系统成功表达并被纯化出可溶性MBP-LMO2-C结合蛋白,利用MBP沉淀技术验证了LMO2-C能与K562细胞中内源性的GATA-1、LDB1结合;哺乳动物双杂交试验进一步证明LMO2-C能与LDB1结合,而且其过表达能够抑制LMO2-L与LDB1的结合,抑制率达(81.13±0.68)%;半定量RT-PCR结果显示在过表达LMO2-C的K562细胞中,GPA基因相对表达水平下调(51.00±1.58)%.结论LMO2-C能结合K562细胞中内源性GATA-1、LDB1蛋白,并能下调红系发育的标志性基因GPA的表达.     

Relationships between trehalose metabolism and maltose utilization in Saccharomyces cerevisiae

Summary A pattern of active accumulation of trehalose during growth on glucose medium, TAC(+) phenotype, is controlled by a polymeric series of maltose fermentation (MAL) genes. An essential requirement for expression of the TAC(+) phenotype is that the MAL gene be in the constitutive state, MAL ^c. Mutation of a constitutive MAL allele to a maltose- inducible or nonfermenting (mal) state, alters the pattern of trehalose metabolism so that little or no trehalose accumulation occurs during growth on glucose medium. The TAC(+) phenotype is obtained in MAL ^c strains whether or not -glucosidase formation is sensitive or resistant to carbon catabolite repression. However, trehalose accumulation is sensitive to glucose levels even in MAL ^c strains in which -glucosidase formation is insensitive to catabolite repression. The effects of constitutive MAL genes on trehalose accumulation cannot be accounted for by an increase in trehalose-6 phosphate synthase or a decrease in trehalase as determined in vitro. A mechanism is proposed in which the gene-product of a MAL gene serves as a common positive regulator for expression of four genes coding respectively for maltose permease, maltase, -methylglucosidase and a component of the trehalose accumulation system.Paper I appeared in Cell. and Molec. Biology 25: 345–354, 1979     

与乙型肝炎病毒preS1特异性结合的HepG2细胞膜受体样蛋白

本文对人肝癌细胞株ＨｅｐＧ２细胞株上与乙型肝炎病毒外周蛋白ｐｒｅＳ１特异性结合的膜受体样蛋白进行了研究。用麦芽糖结合蛋白－ｐｒｅＳ１－直链淀粉树脂亲和层析法，分离得到了与ｐｒｅＳ１特异性结合的ＨｅｐＧ２细胞的膜受体样蛋白质，并经抗ＭＢＰ－ｐｒｅＳ１的单克隆抗体Ｆ３５．２５结合Ｗｅｓｔｅｒｎｂｌｏｔ加以证实。ＳＤＳ－ＰＡＧＥ和ＰＡＧＥ结果显示，ＨｅｐＧ２细胞膜上存在四种不同的受体样蛋白：ＨＬ１，ＨＬ２，ＨＬ３和ＨＬ４，分子量分别为６８０００，６６０００，５１０００和４５０００．对ＨＬ１，ＨＬ２，ＨＬ３和ＨＬ４的氨基末端序列进行了分析。     

Different central opioid receptor subtype antagonists modify maltose dextrin and deprivation-induced water intake in sham feeding and sham drinking rats

Different central opioid receptor subtypes participate in the mediation of intakes of simple (sucrose: μ, κ₁ and complex (maltose dextrin: μ) carbohydrates as well as deprivation-induced water intake (μ) under real-feeding and real-drinking conditions. An identical pattern of μ and κ₁ mediation of sucrose intake was observed in sham-feeding rats as well, suggesting their actions on orosensory mechanisms supporting sucose intake. The present study examined whether centrally administered general (naltrexone: 1–50 μg), μ (β-funaltrexamine: 1–20 μg), μ₁ (naloxonazine: 50 μg), κ₁ (nor-binaltorphamine: 1–20 μg), δ₁ ([d-Ala², Leu⁵, Cys⁶]-enkephalin: 10–40 μg) or δ₂2 (naltrindole isothiocyanate: 20 μg) opioid subtype antagonists altered either maltose dextrin (10%) intake during sham feeding or deprivation (24 h)-induced water intake during sham drinking in rats with gastric fistulas. Sham feeding significantly increased maltose dextrin intake (180%) and sham drinking significantly increased deprivation-induced water intake (256%) over a 60 min time course. Naltrexone significantly and dose-dependently reduced maltose dextrin intake (78%) in sham feeding rats, and deprivation-induced water intake (51%) in sham drinking rats. Maltose dextrin intake in sham feeding rats was significantly reduced by either κ₁ (69%) or δ₁ (59%) opioid antagonism, was significantly increased by μ₁ antagonism (43%), and was not significantly affected by either μ or δ₂ opioid antagonism. Deprivation-induced water intake in sham drinking rats was significantly reduced by either μ (41%), μ₁ (28%), δ₁ (48%) or δ₈ (28%) opioid antagonism, but was not significantly affected by κ₁ opioid antagonism. The difference in opioid receptor subtype mediation of maltose dextrin intake in real feeding and sham feeding conditions suggest that κ₁ and δ₁ receptors are involved in the orosensory mechanisms supporting maltose dextrin intake, while μ receptors are involved in the ingestive and post-ingestive mechanisms supporting maltose dextrin intake. The different patterns of opioid involvement in sucrose and maltose dextrin intake in sham feeding and real feeding conditions provide further support for the hypothesis that at least two different carbohydrate taste systems exist. The difference in opioid receptor subtype mediation of deprivation-induced water intake in real drinking and sham drinking conditions may reflect the removal in the sham drinking condition of a μ-mediated prerestorative satiety mechanism, and the unmasking of other opioid-mediated signalling mechanisms.