Defect in 3'-phosphoadenosine 5'-phosphosulfate synthesis in brachymorphic mice. II. Tissue distribution of the defect.
Defect in 3'-phosphoadenosine 5'-phosphosulfate synthesis in brachymorphic mice. II. Tissue distribution of the defect.
复制标题
短形小鼠中 3-磷酸腺苷 5-磷酸硫酸盐合成缺陷。
DOI：
10.1016/0003-9861(82)90065-0
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发表时间：
1982
影响因子：
3.9
通讯作者：
Schwartz,NB
中科院分区：
文献类型：
--
作者：
Sugahara,K;Schwartz,NB
研究了在短形小鼠软骨中发现的低硫酸化蛋白多糖的生物合成。软骨蛋白聚糖核心蛋白，如通过放射免疫抑制试验测量的类似量，和可比的活性水平的四个糖基转移酶的硫酸软骨素链的合成所需的发现在软骨匀浆从新生儿BM/BM和正常小鼠，表明正常生产的糖基化的核心蛋白受体的硫酸化。当与35 S标记的3′-磷酸腺苷5′-磷酸硫酸盐（PAPS）孵育时，bm/bm软骨提取物显示出高于对照水平的磺基转移酶活性。相反，当合成从ATP和35 SO 42-开始时，突变软骨提取物显示出较低的35 SO 42-掺入内源性硫酸软骨素蛋白聚糖（对照水平的19%），并大大减少PAPS的形成（对照水平的10%）。正常和突变体软骨提取物的共孵育的结果表现出中等水平的硫酸盐掺入PAPS和内源性受体，这表明硫酸盐活化酶或磺基转移酶的抑制剂的情况下。在bm/bm和正常软骨提取物中，35 S]PAPS和35 S标记的腺苷5′-磷酸硫酸盐（APS）的降解速率相当。ATP硫酸化酶（硫酸腺苷酰转移酶; ATP：硫酸腺苷酰转移酶，EC 2.7.7.4）和APS激酶（腺苷酰硫酸激酶; ATP：腺苷酰硫酸3′-磷酸转移酶，EC 2.7.1.25）的特异性测定显示，bm/bm软骨提取物中前者（对照的50%）和后者（对照的10-15%）酶活性降低。这两种酶的活性降低到中等水平的软骨提取物从杂合brachymorphic小鼠（ATP-硫酸化酶，80%的控制; APS激酶，40-70%的控制）。此外，适度减少ATP硫酸化酶活性在BM/BM软骨提取物伴随着增加不稳定性冷冻和解冻的残余活性的这种酶。这些结果表明，在BM/BM软骨中硫酸软骨素蛋白聚糖的硫酸化不足是由于硫酸供体（PAPS）的合成缺陷，这是由于ATP硫酸化酶和APS激酶的活性降低所致，尽管后者的活性降低似乎是PAPS合成缺陷的主要原因。
Biosynthesis of the undersulfated proteoglycan found in brachymorphic mouse (bm/ bm) cartilage has been investigated. Similar amounts of cartilage proteoglycan core protein, as measured by radioimmune inhibition assay, and comparable activity levels of four of the glycosyltransferases requisite for synthesis of chondroitin sulfate chains were found in cartilage homogenates from neonatal bm/bm and normal mice, suggesting normal production of glycosylated core protein acceptor for sulfation. When incubated with35S-labeled 3′-phosphoadenosine 5′-phosphosulfate (PAPS), bm/bm cartilage extracts showed a higher than control level of sulfotransferase activity. In contrast, when synthesis was initiated from ATP and35SO42−, mutant cartilage extracts showed lower incorporation of35SO42−into endogenous chondroitin sulfate proteoglycan (19% of control level) and greatly reduced formation of PAPS (10% of control level). Results from coincubations of normal and mutant cartilage extracts exhibited intermediate levels of sulfate incorporation into PAPS and endogenous acceptors, suggesting the absence of an inhibitor for sulfate-activating enzymes or sulfotransferases. Degradation rates of35S]PAPS and of35S-labeled adenosine 5′-phosphosulfate (APS) were comparable in bm/bm and normal cartilage extracts. Specific assays for both ATP sulfurylase (sulfate adenylyltransferase; ATP:sulfate adenylyltransferase, EC 2.7.7.4) and APS kinase (adenylylsulfate kinase; ATP:adenylylsulfate 3′-phosphotransferase, EC 2.7.1.25) showed decreases in the former (50% of control) and the latter (10–15% of control) enzyme activities in bm/bm cartilage extracts. Both enzyme activities were reduced to intermediate levels in extracts of cartilage from heterozygous brachymorphic mice (ATP-sulfurylase, 80% of control; APS kinase, 40–70% of control). Furthermore, the moderate reduction in ATP sulfurylase activity in bm/bm cartilage extracts was accompanied by increased lability to freezing and thawing of the residual activity of this enzyme. These results indicate that under-sulfation of chondroitin sulfate proteoglycan in bm/bm cartilage is due to a defect in synthesis of the sulfate donor (PAPS), resulting from diminished activities of both ATP sulfurylase and APS kinase, although the reduced activity of the latter enzyme seems to be primarily responsible for the defect in PAPS synthesis.