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 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 Biochemical and cytochemical localization of inosine-5′-diphosphatase in rat liver microsomal fractions

1984 ◽  
Vol 218 (2) ◽  
pp. 501-510 ◽  
Author(s):  
J S Little
Keyword(s):  
Electron Microscope ◽  
Rat Liver ◽  
Incubation Medium ◽  
Microsomal Membrane ◽  
Enzymic Hydrolysis ◽  
Major Fraction ◽  
Cytochemical Localization ◽  
Hydrolysis Of ◽  
Cytoplasmic Side

A procedure has been developed for the biochemical and cytochemical localization of inosine-5′-diphosphatase (IDPase) in rat liver microsomal fractions. The concentration of Pb2+ ions used in the cytochemical incubation medium inhibited IDPase by 32%. IDP formed during the incubation was not hydrolysed further to inosine, and no significant non-enzymic hydrolysis of substrate occurred. When microsomal fractions were incubated cytochemically for IDPase and separated from unchanged substrate under conditions such that the microsomal membrane was not permeable to EDTA, approx. 80% of the reaction product was solubilized by EDTA. In the electron microscope, lead precipitate was observed on the cytoplasmic side (outside) of a major fraction of the vesicles and on the cisternal side (inside) of others. After extraction with EDTA, the lead precipitate was observed only on the cisternal side. Since it was shown that phosphate is trapped on the same side of the membrane as it is released, it is concluded that IDPase can release phosphate on either the cisternal or the cytoplasmic side of the microsomal membrane.

scholarly journals Enzymic hydrolysis of sphingomyelin by rat liver

1966 ◽  
Vol 98 (3) ◽  
pp. 763-769 ◽  
Author(s):  
M Heller ◽  
B Shapiro
Keyword(s):  
Rat Liver ◽  
Enzymic Hydrolysis ◽  
Hydrolysis Of

scholarly journals Cholesterol synthesis in rat liver peroxisomes. Conversion of mevalonic acid to cholesterol.

1987 ◽  
Vol 262 (36) ◽  
pp. 17420-17425 ◽  
Author(s):  
S L Thompson ◽  
R Burrows ◽  
R J Laub ◽  
S K Krisans
Keyword(s):  
Rat Liver ◽  
Cholesterol Synthesis ◽  
Mevalonic Acid ◽  
Liver Peroxisomes

scholarly journals Hydrolysis of Retinol Palmitate by Rat Liver

1966 ◽  
Vol 241 (1) ◽  
pp. 57-64 ◽  
Author(s):  
S. Mahadevan ◽  
N.I. Ayyoub ◽  
O.A. Roels
Keyword(s):  
Rat Liver ◽  
Hydrolysis Of

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.

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