Purification and properties of threonine or allothreonine aldolase from rat liver

Malkin, Leonard I.; Greenberg, David M.

doi:10.1016/0926-6569(64)90172-5

Cited by 26 publications

(26 citation statements)

References 27 publications

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“…These conclusions are different from those of Malkin and Greenberg [5] who claimed that a single enzyme, called by them "threonine or allothreonine aldolase" could split both substrates.…”

Section: Discussioncontrasting

confidence: 54%

“…inhibition of threonim a2dolaae and allothreonine a l d o h e by different wncedrdiona of EDTA. Threonine aldolaee and allothreonine aldoltlse activitiee were measured by the enzymatic method of Malkin and Greenberg [5]. The incubation mixtures had the same composition as indicated in Fig.1, and contained fraction (A) in a concentrations corresponding to 130 mg of freeh tissue per ml, fraction (B) in a concentration correaponding to 1Omg of fresh tissue per ml; EDTA was added a t the concentrations indicated in the abscissae.…”

Section: From the Results Ofmentioning

confidence: 99%

“…Threonine aldolase and allothreonine aldolase activities in the presence of different wncentrdiona of HgCh. Threonine aldolase and allothreonine aldolase activities were measured by the enzymatic method of Makin and Greenberg [5].…”

Section: From the Results Ofmentioning

confidence: 99%

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Threonine Aldolase and Allothreonine Aldolase in Rat Liver

1969

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1.The aldol breakdown of L-threonine and L-allothreonine in rat liver is catalyzed by systems 2. Evidence in presented that two different enzymes, indicated as "threonine aldolase" and localized in the soluble fraction of the homogenate."allothreonine aldolase", are involved in the breakdown of the two amino acids.Braunstein and Vilenkina [l], during studies on the formation of glycine from serine, threonine and other b-hydroxy-a-amino acids in animal tissues, demonstrated the presence of an enzymatic system which cleaves L-threonine and L-allothreonine into acetaldehyde and glycine. Two different enzymes were demonstrated in sheep liver, namely threonine aldolase which catalyzes reversibly the reaction :and allothreonine aldolase which is implicated in another reversible reaction :On the other hand, in rat liver, Malkin and Greenberg [5] showed a unique enzyme, which they called "threonine or allothreonine aldolase", capable of catalyzing the breakdown of both L-threonine and L-allothreonine, and the synthesis of only L-allothreonine [3 -51. We have studied the aldol breakdown of L-threonine and L-allothreonine in rat liver, in order to define the intracellular distribution and properties of the system catalyzing these reaction and to establish whether a single enzyme is responsible for two activities or not.Our experiments gave evidence for the existence of two different enzymes, as in the case of sheep liver. For this reason we prefer the use of the terms "threonine aldolase" and "allothreonine aldolase" instead of the terminology proposed by Malkin and Greenberg [ 5 ] . MATERIALS AND METHODSAdult Wistar strain albino rats weighing about 200 g and fed on a standard laboratory diet were used. The animals were killed by decapitation, the Enzymes. Threonine aldolase (EC 4.1.2.6); allothreonine alclolase (EC 4.1.2.6).livers were washed in 5 volumes of the appropriate solution and homogenized using Potter-Elvehjem apparatus. The pestle operated a t 1,000 rev./min.The technique proposed by DeDuve and coworkers [6] was used to separate the subcellular fractions.I n some experiments liver was homogenized in 0.25 M sucrose, containing I mM EDTA. By differential centrifugation, nuclear, mitochondrial, lysosomal, microsomal and soluble fractions were separated.The nuclear, mitochondrial and lysosomal fractions were washed with 4 ml of the above solution. Nuclei and microsomes were resuspended in 4 volumes of the homogenizing medium per g of fresh liver, while mitochondria and lysosomes were suspended in two volumes per g of liver.I n other experiments the 20°/0 homogenate was prepared in isotonic KCI. I n this case the homogenate was first centrifuged a t 20,000 x g for 20 min; the sediment was discarded ; the supernatant was centrifuged a t 100,000 x g for 60 min. The supernatant thus obtained, was brought up to the initial volume of the homogenate and submitted to differental fractionation procedure with (NH,),SO,.(NH,),SO, fractionations were performed a t 0" by the addition of a saturated solution of (NH,),SO,: Kuni...

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“…These conclusions are different from those of Malkin and Greenberg [5] who claimed that a single enzyme, called by them "threonine or allothreonine aldolase" could split both substrates.…”

Section: Discussioncontrasting

confidence: 54%

Section: From the Results Ofmentioning

confidence: 99%

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Threonine Aldolase and Allothreonine Aldolase in Rat Liver

1969

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“…In vertebrates most L-threonine degradation occurs via the enzymatic activities of serine/threonine dehydratase and threonine dehydrogenase. However, the presence of threonine aldolase enzymatic activity has been demonstrate in rat liver extracts [7-14]. Threonine aldolase contributes 1–3% of total threonine degradation under a variety of nutritional states in both rat and quail [4,15].…”

Section: Introductionmentioning

confidence: 99%

Mice have a transcribed L-threonine aldolase/GLY1 gene, but the human GLY1 gene is a non-processed pseudogene

Edgar

2005

BMC Genomics

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Background: There are three pathways of L-threonine catabolism. The enzyme L-threonine aldolase (TA) has been shown to catalyse the conversion of L-threonine to yield glycine and acetaldehyde in bacteria, fungi and plants. Low levels of TA enzymatic activity have been found in vertebrates. It has been suggested that any detectable activity is due to serine hydroxymethyltransferase and that mammals lack a genuine threonine aldolase.

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“…Several studies have suggested that acetaldehyde is derived not only from ethanol but also from endogenous sources. One proposed pathway is via the cleavage of threonine, which results in acetaldehyde and glycine (Makin and Greenberg, 1964). Indeed, threonine adBlood ministration elevated blood acetaldehyde levels in rats with nonalcoholic liver injury (Ma et al, 1989).…”

mentioning

confidence: 99%