scholarly journals Mechanism of hydroxylation at C-2 during the biosynthesis of ecdysone in ovaries of the locust, Schistocerca gregaria

1984 ◽  
Vol 217 (3) ◽  
pp. 783-789 ◽  
Author(s):  
D R Greenwood ◽  
L N Dinan ◽  
H H Rees
Keyword(s):  
Adult Female ◽  
Schistocerca Gregaria ◽  
Enzymic Hydrolysis ◽  
Ecdysteroid Conjugate ◽  
Hydrolysis Of

The stereochemistry of hydroxylation at C-2 during the biosynthesis of ecdysone in the ovaries of Schistocerca gregaria was investigated by incorporation of [1 alpha,2 alpha-3H(n)]cholesterol in admixture with [4-14C]cholesterol into oöcyte 2-deoxyecdysone and ecdysone conjugates in maturing adult female S. gregaria. Extraction of the eggs followed by enzymic hydrolysis of the ecdysteroid conjugate fraction yielded free ecdysteroids, from which 2-deoxyecdysone and ecdysone were purified. The 3H/14C ratios in the 2-deoxyecdysone and ecdysone were similar, suggesting that the 2 alpha hydrogen of cholesterol was retained during hydroxylation at C-2. This was corroborated by oxidation at C-2 of the 3,22-diacetate derivative of the ecdysone, yielding the corresponding 2-oxo compound with removal of essentially all the 3H originally present at the 2 alpha position of cholesterol. The results indicate that the 2 beta hydrogen of cholesterol has been eliminated during the hydroxylation at C-2. Thus, during ecdysone biosynthesis, hydroxylation at C-2 is direct and occurs with retention of configuration.

scholarly journals Mechanism of hydroxylation at C-22 during the biosynthesis of ecdysteroids in the locust Schistocerca gregaria

1982 ◽  
Vol 208 (3) ◽  
pp. 857-864 ◽  
Author(s):  
D R Greenwood ◽  
H H Rees
Keyword(s):  
Rat Liver ◽  
Adult Female ◽  
Schistocerca Gregaria ◽  
Mevalonic Acid ◽  
Enzymic Hydrolysis ◽  
Hydrogen Atoms ◽  
Hydrolysis Of

1. The fates of the 22-pro-R and 22-pro-S hydrogen atoms of cholesterol during the biosynthesis of ecdysteroids in the ovaries of Schistocerca gregaria were investigated. 2. Two stereospecifically labelled cholesterol species, obtained by incubating 3R,2R- and 3R,2S-[2-14C, 2-3H]mevalonic acid with rat liver preparations, were administered, in turn, to maturing adult female locusts and the radiolabelled ecdysteroid conjugates isolated from the eggs. Enzymic hydrolysis of the conjugates yielded free ecdysteroids, from which ecdysone was purified. 3. Derivative formation and oxidation at C-22 of both ecdysone samples indicated that the 22-pro-R and 22-pro-S hydrogen atoms of cholesterol were stereospecifically eliminated and retained respectively during ecdysteroid formation. This indicates that C-22 hydroxylation in ecdysone biosynthesis is direct and occurs with retention of configuration.

scholarly journals Isolation and identification of 3-acetylecdysone 2-phosphate, a metabolite of ecdysone, from developing eggs of Schistocerca gregaria

1984 ◽  
Vol 217 (1) ◽  
pp. 239-243 ◽  
Author(s):  
R E Isaac ◽  
H P Desmond ◽  
H H Rees
Keyword(s):  
High Performance ◽  
Schistocerca Gregaria ◽  
Helix Pomatia ◽  
Reversed Phase ◽  
Ionization Mass ◽  
Isolation And Identification ◽  
Ecdysteroid Conjugate ◽  
Hydrolysis Of

A major ecdysteroid conjugate, which accumulates in the eggs of the desert locust, Schistocerca gregaria, during the later stages of embryogenesis, has been isolated by reversed-phase and anion-exchange high-performance liquid chromatography. Hydrolysis of the conjugate with a crude arylsulphatase preparation from Helix pomatia liberates mainly ecdysone 3-acetate. The compound was identified as 3-acetylecdysone 2-phosphate by phosphate analysis of an acid-hydrolysed sample, fast atom bombardment, electron impact and chemical ionization mass spectrometry and 1H and 13Cn.m.r. spectroscopy. The instability of 3-acetylecdysone 2-phosphate on storage results in the formation of ecdysone 2-phosphate, which was identified by physicochemical techniques. 3-Acetylecdysone 2-phosphate and ecdysone 2-phosphate are less susceptible than ecdysone 22-phosphate to hydrolysis in vitro by an enzyme preparation from S. gregaria embryos. The possible role of 3-acetylecdysone 2-phosphate as an inactive end product of ecdysteroid metabolism is discussed.

Variation in Quantity of Methanol Recovered from Raisins

1963 ◽  
Vol 46 (2) ◽  
pp. 341-343
Author(s):  
M Alice Brown ◽  
James R Woodward ◽  
Floyd DeEds
Keyword(s):  
Methyl Ester ◽  
Esterase Activity ◽  
Enzymic Hydrolysis ◽  
Methanol Content ◽  
Naturally Occurring ◽  
Pectin Esterase ◽  
Hydrolysis Of

Abstract The amount of naturally occurring methanol in fruit must be known so that the quantity left as fumigation residue can be determined. In a study of methanol content of raisins, which had given inconsistent results, the raisins were subjected to different conditions of treatment immediately prior to methanol determination. Conditions that favored pectin esterase activity gave higher values for methanol content than conditions known to inactivate enzymes. Evidence was also obtained that both chemical and enzymic hydrolysis of methyl ester groups of pectic materials occur during analysis.

scholarly journals Permeability of muscle capillaries to small heme-peptides. Evidence for the existence of patent transendothelial channels.

1975 ◽  
Vol 64 (3) ◽  
pp. 586-607 ◽  
Author(s):  
N Simionescu ◽  
M Siminoescu ◽  
G E Palade
Keyword(s):  
Plasma Proteins ◽  
Intercellular Junctions ◽  
Rat Diaphragm ◽  
Enzymic Hydrolysis ◽  
Graphic Analysis ◽  
Heme Peptides ◽  
Future Work ◽  
Hydrolysis Of ◽  
Muscle Capillaries

Two heme-peptides (HP) of about 20-A diameter (heme-undecapeptide [H11P], mol wt approximately 1900 and heme-octapeptide [H8P], mol wt approximately 1550), obtained by enzymic hydrolysis of cytochrome c, were sued as probe molecules in muscle capillaries (rat diaphragm). They were localized in situ by a perixidase reaction, enhanced by the addition of imidazole to the incubation medium. Chromatography of plasma samples showed that HPs circulate predominantly as monomers for the duration of the experiments and are bound by aldehyde fixatives to plasma proteins to the extent of approximately 50% (H8P) to approximately 95% (H11P). Both tracers cross the endothelium primarily via plasmalemmal vesicles which become progressively labeled (by reaction product) from the blood front to the tissue front of the endothelium, in three successive resolvable phases. By the end of each phase the extent of labeling reaches greater than 90% of the corresponding vesicle population. Labeled vesicles appear as either isolated units or chains which form patent channels across the endothelium. The patency of these channels was checked by specimen tilting and graphic analysis of their images. No evidence was found for early or preferential marking of the intercellular junctions and spaces by reaction product. It is concluded that the channels are the most likely candidate for structural equivalents of the small pores of the capillary wall since they are continuous, water-filled passages, and are provided with one or more strictures of less than 100 A. Their frequency remains to be established by future work.

Investigation of the products of an enzymic hydrolysis of collagens

Biochemistry ◽  
1969 ◽  
Vol 8 (12) ◽  
pp. 4716-4723 ◽  
Author(s):  
Howard B. Bensusan
Keyword(s):  
Enzymic Hydrolysis ◽  
Hydrolysis Of

scholarly journals Constancy of the optimum temperature of an enzyme under varying concentrations of substrate and of enzyme

1914 ◽  
Vol 88 (602) ◽  
pp. 258-262
Keyword(s):  
Experimental Evidence ◽  
Aspergillus Oryzae ◽  
Hydrolytic Enzyme ◽  
Fixed Duration ◽  
Optimum Temperature ◽  
Enzymic Hydrolysis ◽  
Main Interest ◽  
General Law ◽  
The Moment ◽  
Hydrolysis Of

In a recent paper a new enzymic relation is recorded. For the enzymic hydrolysis of salicin—by the enzyme which Gabriel Bertrand and the author have named salicinase —it is found that, in an action of fixed duration, the temperature of greatest activity of the ferment is always the same, whatever the dilutions of substrate and of enzyme adopted for the determination. In other words, the duration of the action being constant, the optimum tem­perature of the ferment is independent of the concentration both of the substrate and of the enzyme. The observation is suggestive: if true of one enzyme it may be true of all, and possibly becomes the enunciation of a general law. Herein, for the moment, lies its main interest. In the present paper further experimental evidence for this hypothesis in given, in the case of another hydrolytic enzyme, the maltase of Aspergillus oryzæ (taka-diastase).

Covalent attachment of amino acids to casein. 1. Chemical modification and rates of in vitro enzymic hydrolysis of derivatives

1979 ◽  
Vol 27 (5) ◽  
pp. 1098-1104 ◽  
Author(s):  
Antoine J. Puigserver ◽  
Lourminia C. Sen ◽  
Elvira Gonzales-Flores ◽  
Robert E. Feeney ◽  
John R. Whitaker
Keyword(s):  
Amino Acids ◽  
Chemical Modification ◽  
Covalent Attachment ◽  
Enzymic Hydrolysis ◽  
Hydrolysis Of
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