scholarly journals Participation of cysteine and cystine in inactivation of tyrosine aminotransferase in rat liver homogenates

1978 ◽  
Vol 176 (2) ◽  
pp. 449-454 ◽  
Author(s):  
W T Buckley ◽  
L P Milligan
Keyword(s):  
Rat Liver ◽  
Tyrosine Aminotransferase ◽  
Particulate Fraction ◽  
Effective Agent ◽  
N2 Atmosphere ◽  
Rapid Inactivation ◽  
Lag Period ◽  
Liver Homogenates

1. Inactivation of tyrosine aminotransferase was studied in rat liver homogenates. Under an O2 atmosphere with cysteine added, inactivation was rapid after a lag period of approx. 1h, whereas a N2 atmosphere extended the lag period to approx. 3h. 2. Replacement of cysteine with cystine resulted in rapid inactivation both aerobically and anaerobically. 3. Removal of the particulate fraction by centrifuging rat liver homogenates at 13,000g for 9min resulted in an aerobic lag period of 0.5h in the presence of cystine and approx. 3h in the presence of cysteine. 4. It is proposed that the stimulatory effect of cysteine on tyrosine aminotransferase inactivation occurs largely as a result of oxidation to cystine, which appears to be a more directly effective agent.

scholarly journals Stabilization of rat liver tyrosine aminotransferase by tetracycline

1975 ◽  
Vol 150 (3) ◽  
pp. 329-333 ◽  
Author(s):  
R Hannah ◽  
M K Sahib
Keyword(s):  
Rat Liver ◽  
De Novo ◽  
Rabbit Antiserum ◽  
Tyrosine Aminotransferase ◽  
Enzyme Inactivation ◽  
Aminotransferase Activity ◽  
Rapid Inactivation ◽  
Liver Homogenates

Rat liver tyrosine aminotransferase was purified 200-fold and an antiserum raised against it in rabbits. 2. Hepatic tyrosine aminotransferase activity was increased fourfold by tyrosine, twofold by tetracycline, 2.5-fold by cortisone 21-acetate and ninefold by a combination of tyrosine and cortisol administered intraperitoneally to rats. 3. Radioimmunoassay with 14C-labelled tyrosine aminotransferase, in conjunction with rabbit antiserum against the enzyme, revealed that cortisol stimulates the synthesis of the enzyme de novo, but that tetracycline has no such effect. 4. Incubation of rat liver homogenates with purified tyrosine aminotransferase in vitro leads to a rapid inactivation of the enzyme, which tetracycline partially inhibits. 5. The inactivation is brought about by intact lysosomes, and the addition of 10mM-cysteine increases the rate of enzyme inactivation, which is further markedly increased by 10mM-Mg2+ and 10mM-ATP. Here again tetracycline partially inhibits the decay rate, leading to the inference that the increase of tyrosine aminotransferase activity in vivo by tetracycline is brought about by the latter inhibiting the lysosomal catheptic action.

O n the Mechanism of Inactivation and ATP-Dependent Reactivation of Rat Liver Tyrosine Aminotransferase

1977 ◽  
Vol 32 (9-10) ◽  
pp. 777-780 ◽  
Author(s):  
Hans-Heinrich Hamm ◽  
Werner Seubert
Keyword(s):  
Rat Liver ◽  
Tyrosine Aminotransferase ◽  
Particulate Fraction ◽  
Kidney Cortex ◽  
Aminotransferase Activity ◽  
Liver And Kidney ◽  
Membrane Bound ◽  
Nucleotide Specificity

Abstract The mechanism of in vitro inactivation and ATP-dependent rapid reactivation of rat liver tyrosine aminotransferase by a membrane-bound system from rat liver and kidney cortex and the nucleotide specificity of this process was investigated using partially purified tyrosine amino­ transferase as a substrate. Adenosine 5′-triphosphate (ATP) could be replaced by guanosine 5′-tri-phosphate (GTP), whereas inosine 5′-triphosphate (ITP) was less effective. During reactivation [γ-32P]A T P was incorporated into the enzyme and not excorporated by incubation of the labeled enzyme with excess non-radioative ATP. Inactivation of labeled tyrosine aminotransferase by a particulate fraction led to a decrease protein-bound radioactivity concomitant with an increase of [32P] orthophosphate. This points to a phosphorylation and dephosphorylation mechanism in the regulation of tyrosine aminotransferase activity.

scholarly journals Subcellular distribution of pyruvate (glyoxylate) aminotransferases in rat liver

1978 ◽  
Vol 170 (1) ◽  
pp. 173-175 ◽  
Author(s):  
T Noguchi ◽  
Y Minatogawa ◽  
Y Takada ◽  
E Okuno ◽  
R Kido
Keyword(s):  
Rat Liver ◽  
Subcellular Distribution ◽  
Enzyme Activities ◽  
Particulate Fraction ◽  
Aminotransferase Activity ◽  
Liver Homogenates ◽  
Glucagon Injection ◽  
Glyoxylate Aminotransferase

The distribution of pyruvate (glyoxylate) aminotransferases in the particulate fraction of rat liver homogenates was examined by centrifugation in a sucrose density graident. Aminotransferase activities towards serine, phenylalanine and histidine with pyruvate and those towards phenylalanine and histidine with glyoxylate were nearly identically distributed. Some 50-55% of the particulate activity was localized in the peroxisomes and the remainder in the mitochondria. Most of alanine-glyoxylate aminotransferase activity was localized in the mitochondria, with some activity in the peroxisomes. Glucagon injection resulted in increases of these enzyme activities in the mitochondria, but not in the peroxisomes.

scholarly journals THE INCORPORATION OF THE CARBOXYL CARBON FROM ACETATE INTO CHOLESTEROL BY RAT LIVER HOMOGENATES

1954 ◽  
Vol 206 (1) ◽  
pp. 471-481 ◽  
Author(s):  
Ivan D. Frantz ◽  
Nancy L.R. Bucher ◽  
Henny S. Schneider ◽  
Naomi H. McGovern ◽  
Ruth Kingston
Keyword(s):  
Rat Liver ◽  
Liver Homogenates ◽  
Carboxyl Carbon

scholarly journals Purification and Properties of Rat Liver Tyrosine Aminotransferase

1969 ◽  
Vol 244 (13) ◽  
pp. 3618-3624 ◽  
Author(s):  
F A Valeriote ◽  
F Auricchio ◽  
G M Tomkins ◽  
D Riley
Keyword(s):  
Rat Liver ◽  
Tyrosine Aminotransferase ◽  
Purification And Properties

scholarly journals Regulation of Tyrosine Aminotransferase in Rat Liver

1973 ◽  
Vol 248 (13) ◽  
pp. 4528-4531
Author(s):  
Ronald W. Johnson ◽  
Francis T. Kenney
Keyword(s):  
Rat Liver ◽  
Tyrosine Aminotransferase

scholarly journals STIMULATION BY DINITROPHENOL OF FORMATION OF MELANIN-LIKE SUBSTANCE FROM TYROSINE BY RAT LIVER HOMOGENATES

1957 ◽  
Vol 225 (2) ◽  
pp. 735-744
Author(s):  
Henry Kamin ◽  
Mildred A. Koon ◽  
Philip Handler
Keyword(s):  
Rat Liver ◽  
Liver Homogenates
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