Horizons in biochemistry and biophysics最新文献_第9页

Structure and function of fibrinogen. 纤维蛋白原的结构和功能。

Horizons in biochemistry and biophysics Pub Date : 1977-01-01

R F Doolittle

引用次数: 0

Recent developments in suicide substrates and other active site-directed inactivating agents of specific target enzymes. 自杀底物和其他特定靶酶活性位点导向灭活剂的最新进展。

Horizons in biochemistry and biophysics Pub Date : 1977-01-01

C Walsh

引用次数: 0

Biochemical aspects of the function of the thymus gland. 胸腺功能的生化方面。

Horizons in biochemistry and biophysics Pub Date : 1977-01-01

G Di Sabato

引用次数: 0

Dynamic aspects of biological membranes. 生物膜的动态方面。

Horizons in biochemistry and biophysics Pub Date : 1977-01-01

A D Keith, W Snipes

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Gout and the regulation of purine biosynthesis. 痛风与嘌呤生物合成的调控。

Horizons in biochemistry and biophysics Pub Date : 1976-01-01

M S Hershfield, J E Seegmiller

{"title":"Gout and the regulation of purine biosynthesis.","authors":"M S Hershfield, J E Seegmiller","doi":"","DOIUrl":"","url":null,"abstract":"Overproduction of purine nucleotides de novo is the cause of hyperuricemia in a substantial portion of the gouty population. Specific enzyme abnormalities--deficiency of hypoxanthine-guanine phosphoribosyltransferase (an enzyme of the purine \"salvage\" pathway) and overactivity of 5- phosphoribosyl-1-pyrophosphate (PP-ribose-P) synthetase--result in hyperuricemia, and are associated with increased de novo purine synthesis and increased intracellular concentrations of PP-ribose-P. The latter is a common substrate for the first enzyme of the de novo pathway (phosphoribosyl amidotransferase) and the purine base salvage enzymes. Studies in cultured cells from patients, and in mutant cells derived from normal cell lines in vitro, suggest that elevated intracellular PP-ribose-P concentrations may increase the rate of de novo purine biosynthesis. This regulation can be explained in terms of the normal intracellular concentration of PP-ribose-P which is lower tthan the Km for the amidotransferase, and by allosteric activation of this enzyme by PP-ribose-P. Feedback inhibition of the first step in the de novo pathway by exogenous purines can be explained either by end-product (nucleotide) inhibition of the amidotransferase, or by competition for PP-ribose-P by the salvage enzymes which have lower Km's for this substrate, or by a combination of these effects. Evidence for and against these mechanisms is discussed. Evidence is presented which suggests that exogenous purines exert a feedback effect, not only on the first step of the de novo pathway, but also at the distal branch point in the pathway. Several potential regulatory mechanisms which might lead to excessive production of uric acid are discussed.","PeriodicalId":75908,"journal":{"name":"Horizons in biochemistry and biophysics","volume":"2 ","pages":"134-62"},"PeriodicalIF":0.0,"publicationDate":"1976-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"11971883","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Mutant methodology in the study of carbohydrate transport. 碳水化合物运输研究中的突变体方法。

Horizons in biochemistry and biophysics Pub Date : 1976-01-01

H L Kornberg, P J Henderson

引用次数: 0

Transfer of substrates across the chloroplast envelope. 底物在叶绿体包膜上的转移。

Horizons in biochemistry and biophysics Pub Date : 1976-01-01

H W Heldt

{"title":"Transfer of substrates across the chloroplast envelope.","authors":"H W Heldt","doi":"","DOIUrl":"","url":null,"abstract":"The chloroplast represents a relatively autonomous metabolic compartment within the plant cell. It is surrounded by an envelope consisting of two membranes of which the inner membrane is the functional barrier. Utilizing the energy of light the chloroplast is able to synthesize dihydroxyacetonephosphate from carbon dioxide and water. To provide the cell with this substrate, inorganic phosphate is required. In the case of phosphate deficiency the product of CO2 fixation may be temporarily stored within the chloroplast as starch. Specific transport processes across the inner envelope membrane permit the transfer of metabolites between the chloroplast and the cytosol. The phosphate translocator facilitates the export of dihydroxyacetone phosphate in exchange for inorganic phosphate. It also catalyzes a shuttle for inorganic phosphate with 3-phosphoglycerate, permitting the indirect transfer of reducing equivalents and of ATP from the chloroplast to the cytosol. The dicarboxylate carrier transporting various dicarboxylates may be suited for the transfer of reducing equivalents from the cytosol into the chloroplast. The ATP translocator, catalyzing a transport of ATP into the chloroplast in exchange for ADP, appears to be important for providing the chloroplast with ATP during the night phase, as required for the mobilization of starch.","PeriodicalId":75908,"journal":{"name":"Horizons in biochemistry and biophysics","volume":"2 ","pages":"199-299"},"PeriodicalIF":0.0,"publicationDate":"1976-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"11971885","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Pancreatic lipase and colipase: an example of heterogeneous biocatalysis. 胰脂肪酶和胶原酶:一个非均相生物催化的例子。

Horizons in biochemistry and biophysics Pub Date : 1976-01-01

M Sémériva, P Desnuelle

{"title":"Pancreatic lipase and colipase: an example of heterogeneous biocatalysis.","authors":"M Sémériva, P Desnuelle","doi":"","DOIUrl":"","url":null,"abstract":"The hydrolytic reactions catalyzed by pancreatic lipase represent a good example of heterogeneous catalysis. The particularity of this enzyme is provided by its preferential action on emulsified substrates. The first step of catalysis resides in a reversible adsorption of the enzyme to the oil-water interface. In fact, the formation of this adsorption complex is an obligatory step for the enzyme to display its full activity. Two principal but not necessarily exclusive hypotheses have been proposed to explain the observed interfacial activation: Either the interface confers new properties on the substrate which allow its subsequent hydrolysis, or the enzyme itself is modified by adsorption at the interface. Different approaches have recently been developed to clarify this point further. The results obtained by chemical modifications of lipase are consistent with the following hypothesis. The active site preexists in solution and becomes fully functional only by interaction of the interface with an additional site on the enzyme molecule which can be tentatively called the \"interfacial activation site.\" Finally, a protein of low molecular weight, colipase, seems necessary for lipase to express its activity under physiological conditions. This protein enters specific interactions with bile salts micelles and is responsible for the reversal of the inhibition of lipolysis brought about by these detergents.","PeriodicalId":75908,"journal":{"name":"Horizons in biochemistry and biophysics","volume":"2 ","pages":"32-59"},"PeriodicalIF":0.0,"publicationDate":"1976-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"11971888","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Carrier-mediated transport of metabolites in mitochondria. 线粒体中代谢物的载体介导运输。

Horizons in biochemistry and biophysics Pub Date : 1976-01-01

A Fonyó, F Palmieri, E Quagliariello

引用次数: 0

The gene expression during the cell life cycle. 基因在细胞生命周期中的表达。

Horizons in biochemistry and biophysics Pub Date : 1976-01-01

P Volpe

引用次数: 0