嗜热脂肪芽孢杆菌高温蛋白酶分解毛发角蛋白的研究

本文研究了嗜热脂肪芽孢杆菌 (Bacillusstearothermophilus)WF - 1 4 6高温蛋白酶对毛发角蛋白的水解作用。结果表明 ,在体积分数为 2 %的巯基乙醇存在的条件下 ,WF - 1 4 6高温蛋白酶对毛发角蛋白有明显的水解作用。对酶解液氨基酸分析表明 ,酶解液中含有对照液中没有的游离蛋氨酸和亮氨酸 ,且游离氨基酸总量是对照样品的 2 .4倍 ,达 1 5 8mg·L-1 。此外 ,酶解液中含有大量的肽     

Utilization of 15N-labelled yeast hydrolysate in Lactococcus lactis IL1403 culture indicates co-consumption of peptide-bound and free amino acids with simultaneous efflux of free amino acids

Lactococcus lactis subsp. lactis IL1403 was grown in medium containing unlabelled free amino acids and ¹⁵N-labelled yeast hydrolysate to gain insight into the role of peptides as a source of amino acids under conditions where free amino acids are abundant. A mathematical model was composed to estimate the fluxes of free and peptide-derived amino acids into and out of the intracellular amino acid pool. We observed co-consumption of peptides and free amino acids and a considerable efflux of most free amino acids during growth. We did not observe significant differences between the peptide consumption patterns of essential and non-essential amino acids, which suggests that the incorporation of a particular amino acid is more dependent on its availability in a readily assimilated form than the organism’s auxotrophy for it. For most amino acids the contribution of peptide-bound forms to the formation of biomass was initially between 30 and 60 % with the remainder originating from free amino acids. During the later stages of fermentation we observed a decrease in the utilization of peptide-bound amino acids, thus indicating that the more readily assimilated peptides are gradually exhausted from the medium during growth.     

Comparative kinetics of appearance in the portal vein of alpha-aminated nitrogen from mixtures of small peptides of free amino acids of the same composition introduced in the duodenum of conscious pigs

The quantitative kinetics of appearance of amino acids (a.a.) in the pig portal vein was studied in 6 animals for 5 hrs. after duodenal perfusion of an enzymatic hydrolysate of milk proteins or a solution of free a.a. of the same composition. Each product was given in two quantities (55 and 110 g). The quantities of a.a. appearing in the portal vein were higher after perfusion of the hydrolysate than after that of the free a.a., independently of the time after the perfusion. Thus, nitrogen present in the small intestine as small peptides is absorbed more quickly than when it is present as free amino acids.     

Effect of hydrophobicity of utilization of peptides by ruminal bacteria in vitro

When mixed ruminal bacteria were incubated with a pancreatic casein hydrolysate and free amino acids of a similar composition, rates of ammonia production were much greater for peptides than for amino acids. The pancreatic digest of casein was then fractionated with 90% isopropyl alcohol. Hydrophobic peptides which dissolved in alcohol contained an abundance of phenolic and aliphatic amino acids, while the hydrophilic peptides which were precipitated by alcohol contained a large proportion of the highly charged amino acids. The Km values of the mixed ruminal bacteria for each fraction were similar (0.88 versus 0.98 g/liter), but the Vmax of the hydrophilic peptides was more than twice that of the hydrophobic peptides (18 versus 39 mg of NH3 per g of bacterial protein per h). Pure cultures of ruminal bacteria had a similar preference for hydrophilic peptides and likewise utilized peptides at a faster rate than free amino acids. Since peptide degradation rates differed greatly, hydrophobicity is likely to influence the composition of amino acids passing unfermented to the lower gut of ruminant animals.     

Effect of hydrophobicity of utilization of peptides by ruminal bacteria in vitro.

When mixed ruminal bacteria were incubated with a pancreatic casein hydrolysate and free amino acids of a similar composition, rates of ammonia production were much greater for peptides than for amino acids. The pancreatic digest of casein was then fractionated with 90% isopropyl alcohol. Hydrophobic peptides which dissolved in alcohol contained an abundance of phenolic and aliphatic amino acids, while the hydrophilic peptides which were precipitated by alcohol contained a large proportion of the highly charged amino acids. The Km values of the mixed ruminal bacteria for each fraction were similar (0.88 versus 0.98 g/liter), but the Vmax of the hydrophilic peptides was more than twice that of the hydrophobic peptides (18 versus 39 mg of NH3 per g of bacterial protein per h). Pure cultures of ruminal bacteria had a similar preference for hydrophilic peptides and likewise utilized peptides at a faster rate than free amino acids. Since peptide degradation rates differed greatly, hydrophobicity is likely to influence the composition of amino acids passing unfermented to the lower gut of ruminant animals.     

蚕蛹水解液的氨基酸分组分离法

采用７３２、７１７树脂对蚕蛹酸水解液进行分离。７３２树脂先将蚕蛹水解液粗略分成酸性、中性、碱性氨基酸,７１７树脂再将中性氨基酸分成甘氨酸－丙氨组酸和亮氨酸－异亮氨酸－缬氨酸组。其中亮、异亮、缬氨酸的含量达到７５．９％;同时还进行了脯氨酸的分离,经７１７树脂分离得到的脯氨酸的含量为５０．６％。     

抗植物病毒农药“病毒煞”的氨基酸成分分析

本文通过对抗植物病毒农药“病毒煞”的氨基酸成分进行分析,共含有１８种氨基酸,其中脯氨酸、谷氨酸、精氨酸和天冬氨酸含量较高,约占水解氨基酸总量的４７％;含有１９种游离氨基酸,脯氨酸含量最高,占游离氨基酸总量的５１％,说明氨基酸可能是其防病增产的有效成分之一。     

Induction of pigmentation in nonproliferating cells of Serratia marcescens by addition of single amino acids

Addition of casein hydrolysate to suspensions of washed, nonpigmented, nonproliferating Serratia marcescens incubating at 27 C induced biosynthesis of prodigiosin. Four amino acids of casein hydrolysate, dl-aspartic acid, l-glutamic acid, l-proline, and l-alanine caused formation of pigment when added individually. dl-Ornithine also was effective. Optimal concentrations for maximal pigmentation were 5 to 10 mg/ml; at these high concentrations, d-serine also induced biosynthesis of some prodigiosin. dl-Alanine and -ornithine were as effective as the l-iosomers, but l-glutamic acid and l-proline gave better responses than their racemic mixtures. Kinetics of prodigiosin biosynthesis after addition of dl-alanine (20 mg/ml) were similar to those of cells suspended in 0.2% casein hydrolysate. The other amino acids were less effective. Addition of 5 mg of dl-alanine or casein hydrolysate per ml to minimal medium increased by 30% the amount of prodigiosin formed by growing cells after incubation for 7 days at 27 C. Cultures grown for 7 days at 27 C in 0.2% casein hydrolsate formed more prodigiosin than did suspensions of nonproliferating cells containing individual amino acids or casein hydrolysate. However, more pigment was produced by cells suspended in l-alanine (5 mg/ml) or l-proline (10 mg/ml) than when suspended in 0.4% natural or synthetic casein hydrolysate. Filtrates from suspensions of nonproliferating cells forming pigment in l-proline induced more rapid formation of prodigiosin, but filtrates from suspensions in dl-alanine did not. The data supported the hypothesis that pyrrole groups of prodigiosin may be synthesized from 5-carbon amino acids such as proline, ornithine, aspartic, and glutamic acids, but the role of alanine is unknown.     

Amino acid production from a sunflower wholemeal protein concentrate

A study was undertaken to investigate the influence of protein concentration and the addition of different doses of endopeptidase (Alcalase) and exopeptidase (Flavourzyme) on the sequential enzymatic hydrolysis of a protein concentrate obtained from defatted sunflower wholemeal. The results show that the greatest degree of hydrolysis (37.8%) is achieved by hydrolyzing an aqueous substrate with a 5% protein concentrate, and using a 0.02 g Alcalase/g of protein concentrate of the substrate. The aminograms performed reveal that the free amino acid found in the highest proportion in the hydrolysate was aspartic acid, which accounted for over 50% of the free amino acids present, regardless of the substrate concentration and the enzyme dosage used. Finally, the hydrolysate obtained from a substrate containing a 5% protein concentrate and a 0.02 g Alcalase/g of protein concentrate displayed characteristics that indicate its suitability for use as a vegetable-origin plant growth regulator.     

Soy and Rapeseed Protein Hydrolysis by the Enzyme Preparation Protosubtilin

A comparative study of soybean and rapeseed protein hydrolysis by protosubtilin, an original Russian enzyme preparation widely used in animal feed production, has been performed. SDS-PAG electrophoresis, HPLC, and mass spectrometry have been employed to analyze the obtained products. The soybean protein isolate used for hydrolysate production was obtained from a commercial supplier, and rapeseed proteins were prepared from the meal by alkali extraction. Low molecular weight impurities were removed by ultrafiltration. The degree of protein hydrolysis has been shown to depend on the substrate-to-enzyme preparation ratio, hydrolysis time, and protein concentration. Rapeseed protein hydrolysis by protosubtilin at an enzyme/protein ratio of 1: 20 and hydrolysis time of 20 h resulted in complete cleavage of the proteins present in the raw material and the accumulation of oligopeptides (molecular weight less than 14 kDa) and free amino acids, which accounted for 53 and 8% of the initial protein weight, respectively. In contrast to rapeseed proteins, soybean proteins showed considerable gelling at the initial stages of hydrolysis, and the formation of insoluble hydrolysis-resistant fragments was observed. The soluble part of the hydrolysate contained short oligopeptides and free amino acids, which accounted for 13% of the initial protein weight only.     

银杏叶中氨基酸的含量测定

本文测定了不同时期采集的银杏树叶中１７种氨基酸的含量。结果表明,银杏叶中水解氨基酸的总含量分别为１５．０９％,１１．８７％,９．９７％,和７．１４％;游离氨基酸的总含量分别为０．７６％,０．２８％。     

Digestion of native collagen, denatured collagen, and collagen fragments by extracts of rat liver lysosomes.

Extracts of highly purified lysosomes from rat liver were examined for their ability to degrade native collagen and thermally denatured collagen at pH values between 3.5 and 7.0. After a 24-h digestion at 36 degrees with the lysosomal extract at a pH of 5.5 or lower (collagen/lysosomal protein; 2/1 or 8/1), both native and denatured collagen were degraded to an extent equivalent to 60 to 70% of that observed upon total acid hydrolysis in 6 N HCl as measured by the ninhydrin reaction (570 nm). At a pH of 6.0, native collagen and denatured collagen were degraded by the mixture of lysosomal proteinases to 11% and 40% of total acid hydrolysis, respectively. At pH 6.5 AND 7.0, the corresponding values were 3% versus 33% and 0.3% versus 11%, respectively. Fragments of collagen (TCA and TCB) are produced when mammalian collagenase degrades native collagen at 25 degrees. These fragments were degraded by the lysosomal extract at 36 degrees to an extent equivalent to 28% and 8% of total acid hydrolysis at pH 6.5 and 7.0, respectively. The experiments at pH 6.5 and 7.0 were done using a collagen/lysosomal protein ratio of 2/1. At pH 5.0 (a pH which is found within secondary lysosomes), the lysosomal extracts degraded collagen to a mixture of free amino acids and small peptides. Amino acid analysis established that approximately 30% of the amino acid residues of the collagen appeared in the lysosomal hydrolysate as free amino acids. Hydroxyproline and perhaps hydroxylysine were the only amino acids found in collagen which did not appear at least to some extent as the free amino acid in this hydrolysate.     

Cadmium,selenium, and tellurium chelators inAspergillus terreus

Aspergillus terreus was cultivated on Harrold's medium supplemented with 0.1% (w/v) cadmium chloride as well as on sulfur free medium amended with 0.1% (w/v) sodium selenite and potassium tellurite separately. The cell free extract of the fungus for each treatment was fractionated on a column packed with Sephadex G 75. The results demonstrated the ability of the fungus to synthesize several cadmium, selenium, and tellurium-binding proteins as well as metallothionein. The results suggested the biosynthesis of heavy metals chelators as well. The amino acids composition of a cadmium-binding metallothionein revealed the presence of high levels of both aromatic and sulfur amino acids in the hydrolysate.     

More monensin-sensitive, ammonia-producing bacteria from the rumen

Two monensin-sensitive bacteria which utilized carbohydrates poorly and grew rapidly on amino acids were isolated from the bovine rumen. The short rods (strain SR) fermented arginine, serine, lysine, glutamine, and threonine rapidly (greater than 158 nmol/mg of protein per h) and grew faster on casein digest containing short peptides than on free amino acids ().34 versus 0.29 h(-1)). Gelatin hydrolysate, an amino acid source containing an abundance of long peptides, was unable to support growth or ammonia production, but there was a large increase in ammonia production if strain SR was cocultured with peptidase-producing ruminal bacteria (Bacteroides ruminicola or Streptococcus bovis). Cocultures showed no synergism with short peptides. Strain SR washed out of continuous culture ().1 h(-1)) at pH 5.9. The irregularly shaped organisms (strain F) deaminated glutamine, histidine, glutamate, and serine rapidly (greater than 137 nmol/mg of protein per min) and grew faster on free amino acids than on short peptides ().43 versus 0.21 h(-1)). When strain F was provided with casein or gelatin hydrolysate and cocultured with peptidase-producing bacteria, there was a more than additive increase in ammonia production. Strain F grew in continuous culture (0.1 h(-1)) when the pH was as low as 5.3. The irregularly shaped cells and short rods were present at less than 10(9)/ml in vivo, but they ahd very high specific activities of ammonia production (greater than 310 nmol of ammonia/mg of protein per min) and could play an important role in ruminal amino acid fermentation.     

猪血蛋白的酶水解及氨基酸含量

以AS1.398中性蛋白酶、胰蛋白酶、木瓜蛋白酶和菠萝蛋白酶对猪血蛋白进行水解,AS1.398中性蛋白酶对猪血蛋白的水解能力最强。采用活性炭对酶水解液进行脱色。脱色后的酶水解液中含有18种氨基酸,必需氨基酸占总氨基酸的39.18%。     

More monensin-sensitive, ammonia-producing bacteria from the rumen.

Two monensin-sensitive bacteria which utilized carbohydrates poorly and grew rapidly on amino acids were isolated from the bovine rumen. The short rods (strain SR) fermented arginine, serine, lysine, glutamine, and threonine rapidly (greater than 158 nmol/mg of protein per h) and grew faster on casein digest containing short peptides than on free amino acids ().34 versus 0.29 h(-1)). Gelatin hydrolysate, an amino acid source containing an abundance of long peptides, was unable to support growth or ammonia production, but there was a large increase in ammonia production if strain SR was cocultured with peptidase-producing ruminal bacteria (Bacteroides ruminicola or Streptococcus bovis). Cocultures showed no synergism with short peptides. Strain SR washed out of continuous culture ().1 h(-1)) at pH 5.9. The irregularly shaped organisms (strain F) deaminated glutamine, histidine, glutamate, and serine rapidly (greater than 137 nmol/mg of protein per min) and grew faster on free amino acids than on short peptides ().43 versus 0.21 h(-1)). When strain F was provided with casein or gelatin hydrolysate and cocultured with peptidase-producing bacteria, there was a more than additive increase in ammonia production. Strain F grew in continuous culture (0.1 h(-1)) when the pH was as low as 5.3. The irregularly shaped cells and short rods were present at less than 10(9)/ml in vivo, but they ahd very high specific activities of ammonia production (greater than 310 nmol of ammonia/mg of protein per min) and could play an important role in ruminal amino acid fermentation.     

The effect of prolonged exposure of pregnant rats to high ambient temperature on several constituents of the genital tract's fluids

1. Various constituents of the genital tract's (GT) fluids were measured in heat-exposed rats (kept for at least 30 days at 35 +/- 1 degree C) and control rats (maintained at 22 +/- 2 degrees C). 2. There were no differences between the groups in the GT fluid volume, protein, free amino acids and glucose contents. 3. Arterial and venous blood glucose levels, pO2 and pH values were similar in both groups. 4. GT fluid protein hydrolysate from heat-exposed rats showed significantly reduced contents of glycine and alanine and elevated contents of valine and lysine as compared with controls. 5. The GT fluid's free amino acid components showed reduced glycine and elevated valine and isoleucine in the heat-exposed group as compared with controls. 6. Progesterone levels in GT fluid of heat-exposed rats was 60% higher than that of controls. 7. It is suggested that the higher progesterone concentration and the altered relative contents of several free amino acids with a possible change in the proteins of the GT fluid may affect the development of the embryo in heat-exposed rats.     

氨基酸显色剂茚三酮试剂的研究（二）──不同浓度显色剂对氨基酸含量的影响

氨基酸显色剂是氨基酸分析的重要试剂之一。主要成份是茚三酮、二甲亚砜、还原剂、氢氧化锂等有机试剂合成的氨基酸显色剂（以下称显色剂）。目前这种显色剂依赖从国外进口,由于受价格、进口周期及有效期限等诸多因素的影响,使之远远不能满足国内用户的需要,为适应国内用户的需要,进一步论证自制显色剂的可行性和可靠性,确定显色剂的最佳配方,本项目对自制显色剂的存放时间［１］、不同浓度显色剂、以及显色剂光学试验等项指标进行了全面系统地分析比较,本研究观察了１００ｍｌ溶液中显色剂含量分别为５ｍｇ、１０ｍｇ、１５ｍｇ、２０ｍｇ、２５ｍｇ等不同浓度的自制和进口显色剂对氨基酸含量的影响,结果表明,当显色剂的浓度为１５ｍｇ／１００ｍｌ时,氨基酸可出现最大峰值、测定所得氨基酸浓度显著高于２０、２５ｍｇ／１００ｍｌ和５、１０ｍｇ／１００ｍｌ所得的结果。提示氨基酸显色剂不但与存放时间有关,而且与其浓度关系密切的有关理论：     

Complex physiology and compound stress responses during fermentation of alkali-pretreated corn stover hydrolysate by an Escherichia coli ethanologen

The physiology of ethanologenic Escherichia coli grown anaerobically in alkali-pretreated plant hydrolysates is complex and not well studied. To gain insight into how E. coli responds to such hydrolysates, we studied an E. coli K-12 ethanologen fermenting a hydrolysate prepared from corn stover pretreated by ammonia fiber expansion. Despite the high sugar content (～6% glucose, 3% xylose) and relatively low toxicity of this hydrolysate, E. coli ceased growth long before glucose was depleted. Nevertheless, the cells remained metabolically active and continued conversion of glucose to ethanol until all glucose was consumed. Gene expression profiling revealed complex and changing patterns of metabolic physiology and cellular stress responses during an exponential growth phase, a transition phase, and the glycolytically active stationary phase. During the exponential and transition phases, high cell maintenance and stress response costs were mitigated, in part, by free amino acids available in the hydrolysate. However, after the majority of amino acids were depleted, the cells entered stationary phase, and ATP derived from glucose fermentation was consumed entirely by the demands of cell maintenance in the hydrolysate. Comparative gene expression profiling and metabolic modeling of the ethanologen suggested that the high energetic cost of mitigating osmotic, lignotoxin, and ethanol stress collectively limits growth, sugar utilization rates, and ethanol yields in alkali-pretreated lignocellulosic hydrolysates.     

Enhancing effect of albumin hydrolysate on ethanol production employing Saccharomyces sake

The enhancing effect of albumin hydrolysate on ethanol production was investigated in ethanol fermentations using Saccharomyces sake. In batchwise ethanol production, addition of supplemental albumin hydrolysate and phosphatidylcholine, or albumin hydrolysate alone, brought about a more than 60% increase in final ethanol concentration (148 or 144 g/L compared with 88 g/L with no supplementation [control] after 72 h). The effect of the supplements is believed to be due to an enhanced alcohol tolerance of cells grown in media containing the supplements. Cells grown in media containing albumin hydrolysate were enriched in phenyalanine, tyrosine, and methionine in their plasma membranes. All three amino acids were also present in considerable amounts in the albumin hydrolysate. This fact suggests that the three amino acids, which are present in albumin hydrolysate, are incorporated into the plasma membranes of cells. Under ethanol production conditions in which only one amino acid among the components of albumin hydrolysate was excluded, namely phenlalanine, tyrosine, or methionine, significant reductions in ethanol production resulted. (c) 1995 John Wiley & Sons, Inc.