The physiological role of L-tyrosine methyl ester sulphotransferase

Abstract

identical with the elongation factors of the supernatant, are present in the ribosomal fraction. These factor(s), presumably, are involved in initiation: however, further investigation is required to elucidate this point. Moreover, preliminary results indicate that a fraction with stimulatory activity similar to that described above can be removed from ribosomes with 0.25M-armmonium chloride. The nature of this fraction is also currently under investigation. In order to investigate the factors that control the reaccumulation of hepatic glycogen after starvation we have measured net rates of glycogen deposition in perfused livers from starved rats. Livers from 170-190g male rats, starved for 48h, were perfused with bicarbonate-albumin-saline, essentially as described by R. Hems, Ross, Berry & Krebs (1966), except that washed erythrocytes from fresh defibrinated rat blood (Baron & Roberts, 1963) were employed, so that haemoglobin was 4% (w/v). Liver samples (0.5g) were taken at 20min (ventral notched lobe) and 50min (large main lobe).When livers from 48h-starved rats were perfused with glucose alone (30mM) glycogen deposition was 0-0.4,umol/min per g wet wt. of liver, but if pyruvate, glycerol and serine (each 5mM) were added after 15min perfusion with 30mM-glucose the glucose concentration in the medium was stabilized and the rate of glycogen accumulation was 0.68+0.05 (10),umol/min per g wet wt. of liver.Unless the glucose concentration in the medium was 25-30mM, glycogen accumulation was less than 0.5,umol/min per g wet wt. of liver and glucose was released into the medium.When liver was perfused under the present conditions with glycerol, pyruvate and serine (each 5mM) in the absence of glucose gluconeogenesis was 1.4,umol/min per g wet wt. of liver for 20-35min, after which the rate decreased. In this experiment average glucose formation between 20-50min was 0.76p mol/min per g wet liver. Rapid

Studies on the sulphation of 3,4-dihydroxyphenylethylamine (dopamine) and related compounds by rat tissues

“…These observations add further support to the conclusions that the enzyme responsible for all these sulpho-conjugations is the L-tyrosine methyl ester sulphotransferase, first described by Mattock & Jones (1970). Barford & Jones (1971b) have in fact proposed that the physiological function of this enzyme is the sulphation of biogenic amines and the affinity of the enzyme for these substrates appears to be similar (W. N. Jenner, unpublished results).…”

Determination and significance of l-tyrosine O-sulphate and its deaminated metabolites in normal human and mouse urine

“…Only when the carboxyl group is blocked and the a-amino group is in an undissociated state can biological sulphation occur (Jones & Dodgson, 1965;Jones et al, 1966) and the existence of a sulphotransferase enzyme, which is able to catalyse the process, has been demonstrated in rat liver cytosol (L-tyrosine methyl ester sulphotransferase; . In fact, it seems probable that the enzyme is normally responsible for the biological sulphation of tyramine (Barford & Jones, 1972). The question must therefore be posed as to the origins of L-tyrosine 0-sulphate in the urine.…”