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首頁(yè)> 美國(guó)衛(wèi)生研究院文獻(xiàn)>Biochemical Journal >Amino ketone formation and aminopropanol-dehydrogenase activity in rat-liver preparations
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Amino ketone formation and aminopropanol-dehydrogenase activity in rat-liver preparations

機(jī)譯:大鼠肝制劑中的氨基酮形成和氨基丙醇脫氫酶活性

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摘要

1. Rat tissue homogenates convert dl-1-aminopropan-2-ol into aminoacetone. Liver homogenates have relatively high aminopropanol-dehydrogenase activity compared with kidney, heart, spleen and muscle preparations. 2. Maximum activity of liver homogenates is exhibited at pH9·8. The Km for aminopropanol is approx. 15mm, calculated for a single enantiomorph, and the maximum activity is approx. 9mμmoles of aminoacetone formed/mg. wet wt. of liver/hr.at 37°. Aminoacetone is also formed from l-threonine, but less rapidly. An unidentified amino ketone is formed from dl-4-amino-3-hydroxybutyrate, the Km for which is approx. 200mm at pH9·8. 3. Aminopropanol-dehydrogenase activity in homogenates is inhibited non-competitively by dl-3-hydroxybutyrate, the Ki being approx. 200mm. EDTA and other chelating agents are weakly inhibitory, and whereas potassium chloride activates slightly at low concentrations, inhibition occurs at 50–100mm. 4. It is concluded that aminopropanol-dehydrogenase is located in mitochondria, and in contrast with l-threonine dehydrogenase can be readily solubilized from mitochondrial preparations by ultrasonic treatment. 5. Soluble extracts of disintegrated mitochondria exhibit maximum aminopropanol-dehydrogenase activity at pH9·1 At this pH, Km values for the amino alcohol and NAD+ are approx. 200 and 1·3mm respectively. Under optimum conditions the maximum velocity is approx. 70mμmoles of aminoacetone formed/mg. of protein/hr. at 37°. Chelating agents and thiol reagents appear to have little effect on enzyme activity, but potassium chloride inhibits at all concentrations tested up to 80mm. dl-3-Hydroxybutyrate is only slightly inhibitory. 6. Dehydrogenase activities for l-threonine and dl-4-amino-3-hydroxybutyrate appear to be distinct from that for aminopropanol. 7. Intraperitoneal injection of aminopropanol into rats leads to excretion of aminoacetone in the urine. Aminoacetone excretion proportional to the amount of the amino alcohol administered, is complete within 24hr., but represents less than 0·1% of the dose given. 8. The possible metabolic role of amino alcohol dehydrogenases is discussed.
機(jī)譯:1.大鼠組織勻漿將dl-1-aminopropan-2-ol轉(zhuǎn)化為氨基丙酮。與腎臟,心臟,脾臟和肌肉的制劑相比,肝臟勻漿具有相對(duì)較高的氨基丙醇脫氫酶活性。 2.在pH9·8時(shí),肝臟勻漿的最大活性。氨基丙醇的Km約為15mm,針對(duì)單個(gè)對(duì)映體計(jì)算,最大活性約為形成9mμmol的氨基丙酮/ mg。濕重肝/小時(shí)在37°氨基丙酮也由左旋蘇氨酸形成,但速度較慢。未知的氨基酮是由dl-4-氨基-3-羥基丁酸酯形成的,其Km約為1。 pH9·8時(shí)200mm。 3.勻漿中的氨基丙醇脫氫酶活性被dl-3-羥基丁酸酯非競(jìng)爭(zhēng)性地抑制,Ki約為3。 200毫米EDTA和其他螯合劑具有微弱的抑制作用,而氯化鉀在低濃度下會(huì)輕微活化,而抑制作用發(fā)生在50-100mm。 4.結(jié)論是氨基丙醇脫氫酶位于線粒體中,與1-蘇氨酸脫氫酶相反,可以通過(guò)超聲處理將其從線粒體制劑中容易地溶解。 5.溶解的線粒體提取物在pH9·1時(shí)顯示最大的氨基丙醇脫氫酶活性。在此pH下,氨基醇和NAD + 的Km值約為5。分別為200和1·3mm。在最佳條件下,最大速度約為形成70mμmol的氨基丙酮/ mg。蛋白質(zhì)/小時(shí)在37°。螯合劑和硫醇試劑似乎對(duì)酶的活性幾乎沒(méi)有影響,但是氯化鉀在測(cè)試到80mm的所有濃度下均具有抑制作用。 dl-3-羥基丁酸酯僅具有輕微的抑制作用。 6. 1-蘇氨酸和dl-4-氨基-3-羥基丁酸酯的脫氫酶活性似乎與氨基丙醇的脫氫酶活性不同。 7.向大鼠腹膜內(nèi)注射氨基丙醇會(huì)導(dǎo)致尿中氨基丙酮的排泄。氨基丙酮的排泄量與氨基醇的攝入量成正比,在24小時(shí)內(nèi)完全排出,但不足所給劑量的0·1%。 8.討論了氨基醇脫氫酶的可能代謝作用。

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