Role of sialic acid in the microheterogeneity of serum thyroxine-binding globulin

Lasne, Françoise; Benzerara, O.; Lasne, Y

doi:10.1016/0167-4838(82)90009-7

Cited by 14 publications

(3 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The present experiments show clearly that the electrophoretic heterogeneity of human prostatic and seminal fluid acid phosphatase is not due solely to the presence of sialic acid, because after total removal of sialic acid at least 4 bands remain apparent in the isoelectric focusing pattern. A similar conclusion has recently been reached for the case of serum thyroxine-binding globulin [29].…”

Section: Discussionsupporting

confidence: 84%

Studies on the structural basis of the heterogeneity of human prostatic and seminal acid phosphatases

1983

View full text Add to dashboard Cite

We studied possible causes of the electrophoretic heterogeneity of the acid phosphatase (EC 3.1.3.2) purified by affinity chromatography from human prostate and human seminal fluid. The isoelectric focusing pattern in polyacrylamide gel shows numerous bands in the pH range 4.0-5.2 and 5.5-5.9. Treatment with neuraminidase under conditions shown to cause complete removal of sialic acid does not abolish the observed heterogeneity. Although there is a change of the more acidic forms to ones having more basic pI values, at least 4 distinct bands remain. Structural differences at the amino terminal end can be ruled out as the cause of the remaining electrophoretic heterogeneity. Lysine is shown to be the amino terminal amino acid for both the prostatic and seminal fluid enzymes. The sequences of the first 23 amino acids are shown to be identical for the prostatic and seminal fluid acid phosphatases. The functional enzyme contains no metal ion but it can be stoichiometrically inactivated by cupric ion.

show abstract

Section: Discussionsupporting

confidence: 84%

Studies on the structural basis of the heterogeneity of human prostatic and seminal acid phosphatases

1983

View full text Add to dashboard Cite

show abstract

“…Hyperestrogenemia, as occurring in pregnant women, is associated with a 2-to 3-fold increase in the serum TBG concentration and a quantitative shift of its IEF bands toward the more heavily sialylated, anodal region (6)(7)(8)(9)(10). In contrast, TBG from subjects with familial TBG elevation has the normal pattern of IEF microheterogeneity, indicating that the pattern is independent of the serum TBG concentration.…”

mentioning

confidence: 70%

“…Microheterogeneity of TBG can be demonstrated by isoelectric focusing (IEF), which shows 5-9 distinct bands at pi 4.1-5.2 (5,6). Results from neuraminadase treatment indicate that these multiple bands represent differences in sialic acid content (6)(7)(8).…”

mentioning

confidence: 98%

Reduced Clearance Rate of Thyroxine-Binding Globulin (TBG) with Increased Sialylation: A Mechanism for Estrogen-Induced Elevation of Serum TBG Concentration*

Ain

Mori

Refetoff

1987

The Journal of Clinical Endocrinology & Metabolism

276

View full text Add to dashboard Cite

Hyperestrogenemic states, including pregnancy, cause an increase in serum T4-binding globulin (TBG) concentrations and an increase in the proportion of TBG molecules with greater anodal mobility on isoelectric focusing, indicating greater sialic acid content. The possible causal relationship between the degree of sialylation and accumulation of TBG in serum was explored by measuring the in vivo half-lives (t1/2) of TBGs with different isoelectric points. TBG in unfractionated serum and its major peaks, isolated by chromatofocusing and defined by their isoelectric points on isoelectric focusing were each injected iv into rats. The resulting TBG concentrations, measured by specific RIA in serum samples obtained at intervals after injection, were used for the calculation of the t1/2. TBG in serum from a pregnant woman had a significantly longer t1/2 of 17.2 +/- 1.2 h (mean +/- SD) compared to those of 13.3 +/- 1.5 and 12.9 +/- 0.9 h for TBG in serum from a man and a nonpregnant woman, respectively. TBG peaks II, III, IV, and V, with increasing anodal mobility, had progressively longer t1/2 values of 11, 13, 15, and 33 h, respectively. However, TBG peaks of the same mobility on IEF isolated from serum of pregnant or nonpregnant subjects had similar t1/2 values. Neither the TBG concentration nor estrogen had a direct effect on the rate of TBG clearance. Indeed, the t1/2 of TBG from a subject with inherited TBG excess was not different from that of TBG from a nonpregnant woman or a man. Chronic treatment of rats with estradiol did not alter the rate of clearance of injected human TBG. Finally, the more heavily sialylated anodal bands of purified but unfractionated serum TBG, analyzed by Western blots, survived longer in the circulation of a rat. These results indicate that the rate of in vivo metabolism of TBG is dependent on its sialic acid content. The increased proportion of TBG molecules with higher sialic acid content thus contributes to the increase in the serum TBG concentration in hyperestrogenemic states.

show abstract

Impaired binding properties of thyroxine-binding globulin in hepatocellular carcinoma and chronic liver disease

et al. 1991

View full text Add to dashboard Cite

To determine the factors underlying the apparent reduction in binding ability of thyroxine-binding globulin in hepatocellular carcinoma, hormone-binding characteristics were further examined in patients with this disease and in control subjects. No differences in affinity constants with respect to triodothyronine or serum thyroxine-binding globulin from hepatocellular carcinoma, cirrhotic and normal subjects were found. The affinity for thyroxine was significantly reduced in hepatocellular carcinoma (0.41 +/- 0.13 x 10(10) mol-1) and cirrhotic (0.65 +/- 0.1 x 10(10) mol-1) patients compared with normal subjects (0.94 +/- 0.7 x 10(10) mol-1). Investigations carried out on liver tissue obtained from patients with hepatocellular carcinoma and chronic liver disease showed that thyroxine-binding globulin within tumor tissue was elevated and bound less exogenous tracer hormone compared with that obtained from nontumor tissue. Tumor-derived thyroxine-binding globulin with altered binding properties is, at least partly, responsible for the abnormal behavior of the serum protein in patients with hepatocellular carcinoma.

show abstract

Role of sialic acid in the microheterogeneity of serum thyroxine-binding globulin

Cited by 14 publications

References 8 publications

Studies on the structural basis of the heterogeneity of human prostatic and seminal acid phosphatases

Studies on the structural basis of the heterogeneity of human prostatic and seminal acid phosphatases

Reduced Clearance Rate of Thyroxine-Binding Globulin (TBG) with Increased Sialylation: A Mechanism for Estrogen-Induced Elevation of Serum TBG Concentration*

Impaired binding properties of thyroxine-binding globulin in hepatocellular carcinoma and chronic liver disease

Contact Info

Product

Resources

About