scholarly journals l-threonine aldolase is not a genuine enzyme in rat liver

1986 ◽  
Vol 237 (1) ◽  
pp. 187-190 ◽  
Author(s):  
Y G Yeung
Keyword(s):  
Lactate Dehydrogenase ◽  
Alcohol Dehydrogenase ◽  
Rat Liver ◽  
Liver Extract ◽  
Threonine Dehydratase ◽  
Threonine Aldolase ◽  
Cytosolic Extract ◽  
Aldolase Activity ◽  
Nadph Dehydrogenase ◽  
Coupled Assay

Activity of L-threonine aldolase in rat liver cytosolic extract was not affected by the omission of alcohol dehydrogenase in a previously established NADPH-linked alcohol dehydrogenase-coupled assay. The liver extract was able to catalyse the dehydrogenation of NADPH with either acetaldehyde (a product of L-threonine aldolase action) or 2-oxobutyrate (a product of L-threonine dehydratase action). When the liver extract was chromatographed on a Sephacryl S-200 column, no threonine aldolase activity was detected in the eluate. However, activity of threonine aldolase re-appeared when the fractions with highest activity of lactate dehydrogenase and threonine dehydratase were mixed. Activity of threonine aldolase could also be abolished by removing threonine dehydratase from the liver extract with a specific antibody. Hence L-threonine aldolase should not be a genuine enzyme in the rat liver, and the apparent enzyme activity may result from a combined effect of threonine dehydratase and lactate dehydrogenase (or an oxo acid-linked NADPH dehydrogenase) in the liver cytosolic extract.

Measurement of l-Threonine Aldolase Activity in Rat Liver

1979 ◽  
Vol 7 (6) ◽  
pp. 1274-1276 ◽  
Author(s):  
MICHAEL I. BIRD ◽  
PETER B. NUNN
Keyword(s):  
Rat Liver ◽  
Threonine Aldolase ◽  
Aldolase Activity

Threonine aldolase and alcohol dehydrogenase activities in Lactobacillus bulgaricus and Lactobacillus acidophilus and their contribution to flavour production in fermented milks

1983 ◽  
Vol 50 (3) ◽  
pp. 375-379 ◽  
Author(s):  
Valerie M. Marshall ◽  
Wendy M. Cole
Keyword(s):  
Alcohol Dehydrogenase ◽  
Dehydrogenase Activity ◽  
Lactobacillus Acidophilus ◽  
Lactobacillus Bulgaricus ◽  
Flavour Compound ◽  
Threonine Aldolase ◽  
Fortified Milk ◽  
Alcohol Dehydrogenase Activity ◽  
Aldolase Activity ◽  
Acetaldehyde Production

SummaryCell-free extracts of both Lactobacillus bulgaricus and L. acidophilus demonstrated threonine aldolase activity, the end product of which was acetaldehyde, the major flavour compound of yoghurt. L. acidophilus also possessed an alcohol dehydrogenase activity capable of reducing acetaldehyde so that little yoghurt flavour was present in milks fermentation with this organism. Addition of threonine to fortified milk before fermentation with L. acidophilus increased acetaldehyde production and resulted in a well flavoured product similar to that of yoghurt made with L. bulgaricus. The contribution of these 2 enzymes to flavour production is discussed.

scholarly journals Metabolic homoeostasis of l-threonine in the normally-fed rat. Importance of liver threonine dehydrogenase activity

1983 ◽  
Vol 214 (3) ◽  
pp. 687-694 ◽  
Author(s):  
M I Bird ◽  
P B Nunn
Keyword(s):  
Dehydrogenase Activity ◽  
High Protein Diet ◽  
Fed State ◽  
Threonine Dehydratase ◽  
Threonine Dehydrogenase ◽  
Threonine Aldolase ◽  
Coa Ligase ◽  
Metabolic States ◽  
Aldolase Activity

Threonine dehydratase, threonine aldolase and threonine dehydrogenase activities were assayed in livers of rats that had been normally-fed, starved for 72 h, fed a high-protein diet or normally-fed and injected with glucagon or cortisone. A modified continuous spectrophotometric assay for threonine aldolase overcame interference resulting from threonine dehydratase activity and revealed that threonine aldolase activity was very low in rat liver, irrespective of the metabolic state of the animal. The concentration of free threonine was determined in livers of animals subjected to the same treatments as described above. Using Michaelis-Menten kinetics to estimate enzyme activities in vivo at intracellular threonine concentrations it was calculated that in the normally-fed state, 87% of the threonine degraded was catabolized by threonine dehydrogenase. In other metabolic states (except in glucagon-treated animals) threonine dehydratase was the major enzyme catalysing threonine catabolism. It was concluded that threonine dehydrogenase activity plays a hitherto unrecognized role in the metabolic homoeostasis of threonine in the normally-fed rat and that this enzyme activity, in association with 2-amino-3-oxobutyrate CoA-ligase, accounts for the known rate of glycine formation from threonine in the rat.

scholarly journals Rat liver alcohol dehydrogenase. Purification and properties

1971 ◽  
Vol 125 (4) ◽  
pp. 1039-1047 ◽  
Author(s):  
M J Arslanian ◽  
E Pascoe ◽  
J G Reinhold
Keyword(s):  
Molecular Weight ◽  
Alcohol Dehydrogenase ◽  
Rat Liver ◽  
Gel Filtration ◽  
Rabbit Antiserum ◽  
Minor Component ◽  
Disc Electrophoresis ◽  
Supernatant Fraction ◽  
Liver Alcohol Dehydrogenase ◽  
A Minor

Alcohol dehydrogenase (EC 1.1.1.1) from the rat liver supernatant fraction has been purified 200-fold and partially characterized. The isolation procedure involved ammonium sulphate fractionation, DEAE-Sephadex chromatography and gel filtration. The purified enzyme behaved as a homogeneous preparation as evaluated by cellulose acetate and polyacrylamide-gel disc electrophoresis. Sulphoethyl-Sephadex chromatography and immunoelectrophoresis with rabbit antiserum indicated the presence of a minor component. Rat liver alcohol dehydrogenase appears to contain 4mol of zinc/mol, has an estimated molecular weight of 65000 and consists of two subunits of similar molecular weight. Heavy-metal ions, thiol-blocking reagents, urea at concentrations below 8m, low pH (5.5) and chelating agents deactivate the enzyme but do not dissociate it into subunits. Deactivated enzyme could not be reactivated. The enzyme is strictly specific for NAD+ and has a broad specificity for alcohols, which are bound at a hydrophobic site. Inhibition occurred with the enzyme equilibrated with Zn2+ at concentrations above 0.1mm.

Formation of acetaldehyde from threonine by lactic acid bacteria

1976 ◽  
Vol 43 (1) ◽  
pp. 75-83 ◽  
Author(s):  
G. J. Lees ◽  
G. R. Jago
Keyword(s):  
Free Amino ◽  
Thiol Group ◽  
Nutritional Requirement ◽  
Threonine Dehydratase ◽  
Threonine Aldolase ◽  
Streptococcus Cremoris ◽  
Dependent Inhibition ◽  
Ph Dependent ◽  
Dehydratase Activity ◽  
Derivatives Of

SummaryGroup N streptococci were found to cleave threonine to form acetaldehyde and glycine. Threonine aldolase, the enzyme catalysing this reaction, was found in all strains exceptStreptococcus cremorisZ8, an organism which had been shown previously to have a nutritional requirement for glycine. The enzyme was strongly inhibited by glycine and cysteine. The inhibition showed characteristics of allosteric inhibition and was pH-dependent. Inhibition by glycine, but not by cysteine, was highly specific. Analogues and derivatives of cysteine which contained a thiol group and a free amino group inhibited the activity of threonine aldolase. The presence of a carboxyl group was not necessary for inhibition. The cleavage of threonine by wholecell suspensions was stimulated by either an energy source to aid transport, or by rendering the cells permeable to substrate with oleate. Threonine did not appear to be degraded by enzymes other than threonine aldolase, as threonine dehydratase activity was low and NAD- and NADP-dependent threonine dehydrogenases were absent.

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