Transverse gradient electrophoresis: protein homogeneity test and subfractionation technique

Electrophoresis of protein (including enzyme) was conducted in a gel medium across which, transverse to the direction of protein migration, a continuous (p)H gradient extends. Any splitting of a resultant trace for the change of protein mobility with (p)H suggests both protein heterogeneity and the (p)H conditions under which further purification and subfractionation may best be pursued.     

Horseshoe crab lactate dehydrogenases: evidence for dimeric structure

D-Lactate dehydrogenase of Limulus polyphemus occurs in six molecular forms, not in five as does the L-lactate dehydrogenase of vertebrates. The electrophoretic pattern of bands in an apparent genetic variant is incompatible with a model of tetrameric molecular structure, and suggests, rather, that the three more anodally migrating isozymes are dimer molecules, the polypeptide subunits of which are encoded by two genetic loci and are not involved in the formation of the lower triad of isozymes.     

Rabbit lactate dehydrogenase isozymes: effect of pH on activity

The ability of lactate dehydrogenase isozyme five from rabbit skeletal muscle to catalyze pyruvate reduction is extremely sensitive to changes of pH within the range of 6.2 to 7.8.The activity of lactate dehydrogenase isozyme one from rabbit heart is virtually unaffected by changes of pH within the same range. Isozyme five is activated by low concentrations of oxalacetate and inhibited by higher concentrations, but other substrates of the citric acid cycle have no effect.     

Enzyme-coenzyme complexes of pyridine nucleotide-linked dehydrogenases

Enzyme-reduced coenzyme binary complexes produce previously unreported shifts in the spectrum of the free coenzyme. These shifts give rise to difference spectra which resemble a general environmental change for reduced diphosphopyridine nucleotide (DPNH) in the glutamic dehydrogenase-DPNH complex, and indicate a more specific enzyme-coenzyme interaction for yeast alcohol dehydrogenase-DPNH, isocitrate dehydrogenase-TPNH, and lactic dehydrogenase-DPNH complexes.     

Lactate dehydrogenase isozymes: dissociation and denaturation by dilution

The tetrameric enzyme lactate dehydrogenase dissociates into its constituent monomeric subunits in a high ion to protein concentration ratio, in certain ionic environments when frozen, and at extreme dilution. Dissociation by dilution involves changes in tertiary conformation which inactivate the enzyme. The dissociation is strongly inhibited by homologous native proteins, but only slightly by denatured or unrelated proteins.     

Lactate dehydrogenase isozymes: kinetic properties at high enzyme concentrations

The kinetic properties of lactate dehydrogenase (LDH) isozymes have been determined at high enzyme concentrations. Spectrophotofluorometric assays revealed that the extent of substrate inhibition of LDH-1 and LDH-5 depends on enzyme concentration. At high enzyme concentrations, in the range of those that exist in most mammalian cells, no inhibition by pyruvate occurred. Pyruvate concentrations up to and including 20.0 millimoles per liter were used for each isozyme at 25 degrees and 40 degrees C at pH 7.0 and 7.4. These results suggest that substrate inhibition of LDH may not occur in vivo but only in vitro after appreciable dilution from physiologic enzyme concentrations. These experiments provide further evidence against the theory that substrate inhibition of LDH-1 in vivo accounts for the distribution of LDH isozymes within various tissues. They raise the possibility that, for other enzymes, kinetic properties determined at highly dilute concentrations in vitro may also be quite different from kinetic properties at the much higher concentrations that exist in vivo.     

Alcohol dehydrogenase in maize: genetic basis for multiple isozymes

There are two distinct sets of alcohol dehydrogenase isozymes from maize, but they have subunits in common. Induced mutations at the (Adh(1)) locus altered the migration rate of both Set I and Set II isozymes.     

泡菜中高产乳酸功能性乳酸菌的筛选

乳酸菌是生物体中有益菌的重要组成,筛选出产酸能力强、能够起到肠道医生作用且安全性高的乳酸菌,并应用于相关发酵产品生产对生物健康至关重要.该研究通过碳酸钙-MRS透明圈法从酸菜中筛选乳酸菌,利用对羟基联苯法测定乳酸菌发酵液中乳酸含量,选取产乳酸超过30mg/mL的菌株4株作为候选菌株,对其进行常见致病菌的抑菌能力和十大类常见抗生素的药物耐受性的测定.结果表明,备选菌株对常见致病菌均具有一定的抑菌性能,其中2个菌株在抗生素耐药性方面表现出了较好的安全性.筛选出的2株菌株的产酸性能强,肠道有害菌抑菌效果明显,安全性高.     

Lactate dehydrogenase isozymes: further kinetic studies at high enzyme concentration

In the report "Lactate dehydrogenase isozymes: Further kinetic studies at high enzyme concentration" by Thomas Wuntsch, Raymond F. Chen, and Elliot S. Vesell [169, 480 (1970)], 14.0 mM NAD in line 2 of the heading of Table 1 should read 14.0 , microM NAD.     

花生种子脂肪氧化酶同工酶鉴定研究

根据花生种子脂肪氧化酶同工酶等电点差异,利用等电聚焦电泳技术,对不同品种花生种子脂肪氧化酶同工酶进行鉴定分析。结果表明:(1)花生种子脂肪氧化酶同工酶有4条带,其等电点分别为pH6.35、pH7.00、pH7.46、pH7.74;(2)不同品种花生种子脂肪氧化酶的IEF-PAGE图谱有差异,其中三份材料呈现4条酶带,其它材料呈现3条酶带;(3)相同类型不同品种种子脂肪氧化酶的电泳图谱不同。     

Lactate dehydrogenase isozymes: further kinetic studies at high enzyme concentration

By competition with lactate dehydrogenase (LDH) for nicotinamide adenine dinucleotide (NAD), commonly occurring intracellular proteins, such as glyceraldehyde-3-phosphate dehydrogenase, malate dehydrogenase, and albumin, can protect LDH-1 and LDH-5 from inhibition and ternary complex formation with NAD and pyruvate. The existence of intracellular proteins that compete with LDH for NAD renders unphysiological a model for estimating the extent of intracellular LDH inhibition based on incubations of only LDH, NAD, and pyruvate.     

Physiological concentrations of lactate dehydrogenases and substrate inhibition

Lactate dehydrogenases at physiological concentrations are inhibited by high concentrations of pyruvate when the enzyme and the pyruvate are incubated in the presence of oxidized nicotinamide-adenine dinucleotide before assay. The inhibition is much more pronounced with the H-type than with the M-type lactate dehydrogenase. These results suggest that substrate inhibition may be operative in vivo.     

Conservation and duplication of isozymes in plants

Many enzymes in plants have isozymes because the same catalytic reaction is often present in several subcellular compartments, most frequently the plastids and the cytosol. The number and subcellular locations of the isozymes appear to be highly conserved in plant evolution. However, gene duplication in diploid species and the addition of genomes in polyploid species have increased the number of isozymes.     

铝胁迫对大豆酯酶同工酶的影响

采用聚丙烯酰胺凝胶电泳，研究了3个大豆品种两个不同生长时期在铝胁迫下酯酶同工酶酶谱的变化情况。结果表明，幼苗期3个品种的酶活性和酶带数量随着铝浓度的增加变化不一，但总趋势为下降。三叶期3个品种的酶活性和酶带数量随着铝浓度的增加变化不明显，这与各品种对铝胁迫的适应性密切相关。     

产细菌素乳酸菌的筛选

[目的]开发出更加高效、抑菌谱更广、可做天然防腐剂的细菌素。[方法]以泡菜、酸奶为原料,利用MRS选择培养基从试材中筛选出能够抑制指示菌的细菌,通过排除酸抑制作用、过氧化氢抑制作用和蛋白酶敏感性试验证明该菌株是否产生有抑菌作用的细菌素。[结果]筛选得到的菌株经鉴定证明是乳酸菌,其产生的细菌素对革兰氏阴性菌和革兰氏阳性菌都有抑制作用,是一株产广谱细菌素的乳酸菌。[结论]筛选得出的乳酸菌细菌素在抑制各种病原菌和食品腐败等方面具有重要作用。     

一株乳酸杆菌的选育

利用MRS培养基从酸奶中分离出1株乳酸菌,并用经典分离法对所分离的乳酸菌菌株进行系统的细菌学鉴定和生物学特性研究。经初步鉴定该菌株为乳酸菌属。对其进行生长曲线、pH及酸度的测定结果显示,分离乳酸菌的对数生长期为18 h;培养以后pH下降达到稳定;酸度较高的产酸时间为前18 h。该菌株生长速度快,产酸量高,适合作为发酵饲料的菌种。     

虾夷扇贝同工酶的生化遗传分析

用聚丙烯酰胺凝胶不连续电泳,对虾夷扇贝Patinopecten yessoensis的闭壳肌、外套膜、消化盲囊、鳃和性腺5种组织中CAT、MDH、SOD、ME、EST、α～AMY、ADH、ACP和ALP9种同工酶的表达情况进行了分析,记录了20个基因座位,其中8个为多态。并分析了SOD酶谱带特征及虾夷扇贝遗传变异情况。     

Lactate dehydrogenase isozymes of chick embryo: response to variations of ambient oxygen tension

Incubation of chick embryos in an hypoxic environment causes an ncrease in the proportion of tissue lactate dehydrogenase (LDH) made up of subunit M, whereas incubation in aerobic conditions decreases the proportional amount of subunit M. The variation of ambient oxygen tension does not change the total LDH activity. These results support the hypothesis that oxygen or oxidative metabolites have an effect on the synthesis of the subunit peptides.