Insect extramitochondrial glycerophosphate dehydrogenase II. Enzymic properties and amino acid composition of the enzyme from honeybee (Apis mellifera) thoraces
{"title":"Insect extramitochondrial glycerophosphate dehydrogenase II. Enzymic properties and amino acid composition of the enzyme from honeybee (Apis mellifera) thoraces","authors":"Ronald W. Brosemer, Ronald R. Marquardt","doi":"10.1016/0926-6593(66)90007-5","DOIUrl":null,"url":null,"abstract":"<div><p>Several enzymic properties of crystalline honeybee (<em>Apis mellifera</em>) thoracic glycerophosphate dehydrogenase (<span>L</span>-glycerol-3-phosphate:DPN<sup>+</sup> oxidoreductase, EC 1.1.1.8) were determined. The apparent Michaelis constant for dihydroxyacetone phosphate is 0.33 mM; there is no increase in activity with substrate concn. above 0.5 mM.</p><p>The bee enzyme has a broad pH optimum around pH 6.6, while the rabbits-muscle enzyme has a sharp optimum at pH 7.7. The bee enzyme is stable for 15 min at 21° from pH 4.8 to 9.9.</p><p>The temperature coefficient, <span><math><mtext>Q</mtext><msub><mi></mi><mn>10</mn></msub></math></span>, for the bee enzyme is 1.7 in the range from 21° 36°. The enzyme is stable for 5 min at 55° and completely inactivated at 61°. The bee enzyme shows the same relative reactivity with 2 DPN<sup>+</sup> analogues as does the rabbit enzyme. The bee enzyme is inhibited by a low concentration of <span><math><mtext>p-</mtext><mtext>mercuribenzoate</mtext></math></span> (PCMB), is less sensitive to <span><math><mtext>N-</mtext><mtext>ethylmaleimide</mtext></math></span>, and is not inhibited by 1 mM iodoacetate. Glutathione does not activate the enzyme.</p><p>The amino acid composition of the bee enzyme is quite different from the previously reported composition of the rabbits-muscle enzyme. The minimum molecular weight of the bee enzyme based on 1 tryptophan residue is 32 700. Since the molecular weight determined on a Sephadex G-200 column is around 67 000, the amino acid composition indicates a mol. wt. of 65 400.</p></div>","PeriodicalId":100160,"journal":{"name":"Biochimica et Biophysica Acta (BBA) - Enzymology and Biological Oxidation","volume":"128 3","pages":"Pages 464-473"},"PeriodicalIF":0.0000,"publicationDate":"1966-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0926-6593(66)90007-5","citationCount":"37","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Biochimica et Biophysica Acta (BBA) - Enzymology and Biological Oxidation","FirstCategoryId":"1085","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/0926659366900075","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 37
Abstract
Several enzymic properties of crystalline honeybee (Apis mellifera) thoracic glycerophosphate dehydrogenase (L-glycerol-3-phosphate:DPN+ oxidoreductase, EC 1.1.1.8) were determined. The apparent Michaelis constant for dihydroxyacetone phosphate is 0.33 mM; there is no increase in activity with substrate concn. above 0.5 mM.
The bee enzyme has a broad pH optimum around pH 6.6, while the rabbits-muscle enzyme has a sharp optimum at pH 7.7. The bee enzyme is stable for 15 min at 21° from pH 4.8 to 9.9.
The temperature coefficient, , for the bee enzyme is 1.7 in the range from 21° 36°. The enzyme is stable for 5 min at 55° and completely inactivated at 61°. The bee enzyme shows the same relative reactivity with 2 DPN+ analogues as does the rabbit enzyme. The bee enzyme is inhibited by a low concentration of (PCMB), is less sensitive to , and is not inhibited by 1 mM iodoacetate. Glutathione does not activate the enzyme.
The amino acid composition of the bee enzyme is quite different from the previously reported composition of the rabbits-muscle enzyme. The minimum molecular weight of the bee enzyme based on 1 tryptophan residue is 32 700. Since the molecular weight determined on a Sephadex G-200 column is around 67 000, the amino acid composition indicates a mol. wt. of 65 400.