The effect of elevated temperatures on the mimosine content and toxicity of koa haole (Leucaena glauca)

When koa haole leaves were stored at elevated temperatures the mimosine content was decreased. The effect was most pronounced and rapid when the temperature was over 70 °C. in the presence of moisture. A similar effect occurred in seeds when sufficient moisture was present. The phenomenon did not take place in dry leaves. Steam was effective in extracting mimosine from koa haole leaves.Heated koa haole leaf meal has been demonstrated to be less toxic than unheated koa haole leaf meal when the meals are fed to albino rats as part of their rations. The development of alopecia in rats fed unheated koa haole meal has been described, and the growth curves of rats fed heated and unheated leaf meals and basal rations have been compared.Ferrous sulfate added to rations containing unheated koa haole leaf meal has been shown to be effective in reducing mimosine toxicity.     

骆驼蓬提取物对豌豆幼苗生长的影响

用不同浓度的骆驼蓬提取物处理豌豆种子,明显导致幼苗根系活力及叶绿素和叶片可溶性蛋白质含量下降,膜透性增加。分析表明,骆驼蓬提取物处理下幼苗叶片膜脂过氧化作用增强;过氧化物酶(POD)活性提高;而超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性降低。     

Enzymic alanylation of an isoxazolinone glucoside by legume seedling extracts

Enzymic synthesis of the natural product β-(2-β-d-glucopyranosyl-3-isoxazolin-5-on-4-yl) alanine is described, using the natural isoxazolinone glucoside and O-acetyl-l-serine as substrates and extracts from seedlings as enzyme preparations. Lathyrus odoratus extracts show a higher activity than those of Pisum sativum, Citrullus vulgaris and Leucaena leucocephala.     

The formation of serine from glycine and formaldehyde by cell free extracts of Clostridium acidi-urici.

Cells of Clostridium acidi-urici which were grown in a medium containing uric acid were harvested, disrupted by sonication and centrifuged. After centrifugation the supernatant which served as the cell free extract was used to study the synthesis of serine from 2-14C glycine and formaldehyde. Serine was isolated from the reaction mixture by column chromatography. After identification by paper chromatography, serine was degraded carbon by carbon to locate the position of the labelled carbon. Radioactivity was confined almost exclusively to the alpha carbon of serine which was derived from the alpha carbon of glycine. Formaldehyde, therefore, binds at the alpha carbon of glycine to form serine. Conversion of serine to pyruvate was prevented by adding EDTA to the reaction mixture.     

Cyanide formation from glyoxylate and hydroxylamine catalysed by extracts of higher-plant leaves

Extracts of spinach, maize and barley contain an enzyme which catalyses the formation of hydrogen cyanide from glyoxylate and hydroxylamine. The enzyme is dependent upon ADP and a divalent cation such as manganese. Glyoxylicacid oxime is a poor substrate for the enzyme. Carbon dioxide is another product of the reaction and is probably produced in 1:1 stoichiometry with hydrogen cyanide. The possible relationship of this enzyme to the regulation of nitrate reduction is discussed.     

The metal-mediated formation of hydroxyl radical by aqueous extracts of cigarette tar

Aqueous extracts of cigarette tar produce hydroxyl radicals that are spin trapped by 5,5-dimethyl-1-pyrroline-N-oxide. The addition of catalase almost completely inhibits and superoxide dismutase partially inhibits spin adduct formation. The addition of ethylenediamine tetraacetic acid greatly increases the amount of hydroxyl radical adduct observed; in contrast, diethylenetriamine pentaacetic acid causes complete inhibition of spin adduct formation. We suggest that the hydroxyl radical arises from the metal-mediated decomposition of hydrogen peroxide, and that hydrogen peroxide is formed from the reduction of dioxygen by the semiquinones present in the cigarette tar.     

Ethylene formation by cell-free extracts of Escherichia coli

The pathway leading to the formation of ethylene as a secondary metabolite from methionine by Escherichia coli strain B SPAO has been investigated. Methionine was converted to 2-oxo-4-methylthiobutyric acid (KMBA) by a soluble transaminase enzyme. 2-Hydroxy-4-methylthiobutyric acid (HMBA) was also a product, but is probably not an intermediate in the ethylene-forming pathway. KMBA was converted to ethylene, methanethiol and probably carbon dioxide by a soluble enzyme system requiring the presence of NAD(P)H, Fe³⁺ chelated to EDTA, and oxygen. In the absence of added NAD(P)H, ethylene formation by cell-free extracts from KMBA was stimulated by glucose. The transaminase enzyme may allow the amino group to be salvaged from methionine as a source of nitrogen for growth. As in the plant system, ethylene produced by E. coli was derived from the C-3 and C-4 atoms of methionine, but the pathway of formation was different. It seems possible that ethylene production by bacteria might generally occur via the route seen in E. coli.Abbreviations EDTA ethylenediaminetetraacetic acid - HMBA 2-hydroxy-4-methylthiobutyric acid (methionine hydroxy analogue) - HSS high speed supernatant - KMBA 2-oxo-4-methylthiobutyric acid - PCS phase combining system     

p-Cresol formation by cell-free extracts of Clostridium difficile

Cell-free extracts of Clostridium difficile were shown to form p-cresol by decarboxylation of p-hydroxyphenylacetic acid. This activity required both high and low molecular weight fractions. The active component of the low molecular weight fraction had properties of an amino acid and could be replaced by serine, threonine or the corresponding alpha keto acids. Pyruvate was shown to function catalytically. Since the high molecular weight fraction was O₂-sensitive and since dithionite was as effective as pyruvate with some high molecular weight fractions, the alpha keto acids probably serve as low potential reducing agents in this system. Because of instability, the p-cresolforming enzyme could not be purified.