scholarly journals Hydroxyproline and proline inhibit α-amylase from isolated barley aleurone layers

2014 ◽  
Vol 52 (3-4) ◽  
pp. 253-263 ◽  
Author(s):  
Craig C. Freudenrich ◽  
William V. Dashek
Keyword(s):  
Carboxylic Acid ◽  
Hordeum Vulgare ◽  
Gibberellic Acid ◽  
Glutamic Acid ◽  
Incubation Medium ◽  
Amylase Activity ◽  
Membered Ring ◽  
Pipecolic Acid ◽  
Enzyme Substrate ◽  
Barley Aleurone

Previously, we reported that 1 mM hydroxyproline appeared to inhibit the gibberellic acid-induced release of α-amylase from isolated <em>Hordeum vulgare</em> L. cv. Himalaya aleurone layers into an incubation medium. Here, we report our attempts to determine the mechanism(s) for this inhibition and whether this inhibition can be caused by other proline analogues. Both 1 mM hydroxyproline and proline inhibited extracellular a-amylase activity without affecting its intracellular activity. This suggested that neither hydroxyproline nor proline impaired the release of a-amylase. Lineweaver-Burk plots revealed that both hydroxyproline and proline uncompetitively inhibited α-amy-lase. Thus, the inhibition is probably an assay artifact resulting from the formation of an enzyme-substrate-hydroxyproline or -proline complex. Because azetidine-2-carboxylic acid, glutamic acid and pipecolic acid did not inhibit extracellular α-amylase activity, the uncompetitive inhibition of a-amylase must be unique to imino aicids as well as their precursors and derivatives which possess a five membered ring.

Induction of Sensitivity to Gibberellic Acid in Developing Wheat Caryopses: Effect of Rate of Desiccation

1979 ◽  
Vol 6 (2) ◽  
pp. 229 ◽  
Author(s):  
PB Nicholls
Keyword(s):  
Relative Humidity ◽  
Gibberellic Acid ◽  
Incubation Medium ◽  
Amylase Activity ◽  
Dry Out

No change in the total β-amylase activity, attributable to the presence of 10-6 M gibberellic acid (GA3) in the incubation medium, was found in freshly harvested, de-embryonated, immature (11-38 days post-anthesis) caryopses of wheat. Significant amounts of GA3-induced α-amylase activity was found in 26-h incubates of similar caryopses which had been allowed to dry out either in the ear or detached from the ear. After 10 days of storage of detached immature caryopses in air of 99-100% relative humidity, de-embryonated half-caryopses responded to applied GA3 by producing α-amylase. More α-amylase was found in 26-h incubates if detached caryopses dried out slowly, but rapid desiccation led to little or no α-amylase being produced in the presence of GA3. Caryopses taken from ears cultured on 0.4 or 4% sucrose for 10 days did not respond to applied GA3 whereas those from ears cultured on water did respond, although the amount produced in 26-h incubates was not as large as those from slowly dried ears. Development of the ability to respond to GA3 by increasing α-amylase activity depended on the duration of desiccation or isolation from the plant. Changes in metabolism emanating from the interruption to the supply of sucrose to the caryopsis may be involved in the development of the ability of the aleurone to respond to GA3.

Herbicidal Influence on Amylase in Barley and Squash Seedlings

Weed Science ◽  
1968 ◽  
Vol 16 (4) ◽  
pp. 519-522 ◽  
Author(s):  
Donald Penner
Keyword(s):  
Hordeum Vulgare ◽  
Carbon Source ◽  
Gibberellic Acid ◽  
Dicarboxylic Acid ◽  
Amylase Activity ◽  
Culture Solution ◽  
Cucurbita Maxima ◽  
Simultaneous Addition ◽  
Carbohydrate Degradation ◽  
Low Levels

The development of amylase activity controlled by the embryo in the distal halves of intact barley (Hordeum vulgareL., var. Larker) seeds during the first 2 days of germination was prevented by the presence in the culture solution of 10−4M 7-oxabicyclo-(2.2.1)heptane-2,3-dicarboxylic acid (endothall), 3,5-dibromo-4-hydroxybenzonitrile (bromoxynil), 2,6-dichlorobenzonitrile (dichlobenil), or 3 amino-2,5-dichlorobenzoic acid (amiben) and was not overcome by the simultaneous addition of gibberellic acid. The aforementioned herbicides did not inhibit gibberellic acid-induced amylase synthesis in de-embryonated halved barley seeds. The amiben and bromoxynil inhibition of barley germination was slightly reduced by the simultaneous addition of 10−2M glucose to the culture solution. Amiben and bromoxynil also inhibited the development of low levels amylase activity found in 2-day-old squash (Cucurbita maximaDuchesne, var. Chicago Warted Hubbard) cotyledons; however, added benzyladenine overcame the inhibition. In contrast to barley, benzyladenine was shown to induce the development of amylase activity in squash. Tolerance of squash and other seeds low in carbohydrates to amiben and bromoxynil during germination may be related to their independence from herbicide-inhibited carbohydrate degradation for energy and carbon source required for anabolic processes.

scholarly journals Electrophilic boron carboxylate and phosphinate complexes

2019 ◽  
Vol 48 (6) ◽  
pp. 2038-2045 ◽  
Author(s):  
Diya Zhu ◽  
James H. W. LaFortune ◽  
Rebecca L. Melen ◽  
Douglas W. Stephan
Keyword(s):  
Carboxylic Acid ◽  
Membered Ring ◽  
Ring Species ◽  
Derivatives Of

A series of carboxylic acid derivatives of the form [RC(O)OB(C6F5)]2O, (R = Tol, Ph, C6F5, Me2BrC, Me) were prepared with the concurrent reduction to the corresponding aldehyde. The mechanism is proposed to proceed via cyclic eight-membered ring species.

scholarly journals N-(5′-Phosphopyridoxyl)glutamic acid and N-(5′-phosphopyridoxyl)-2-oxopyrrolidine-5-carboxylic acid and their action on the apoenzyme of aspartate aminotransferase

1971 ◽  
Vol 124 (1) ◽  
pp. 99-106 ◽  
Author(s):  
R M. Khomutov ◽  
H B. F. Dixon ◽  
L V. Vdovina ◽  
M P. Kirpichnikov ◽  
Y V. Morozov ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Carboxylic Acid ◽  
Glutamic Acid ◽  
Aspartate Aminotransferase ◽  
Fluorescence Spectra ◽  
Pyridoxal Phosphate ◽  
Hydroxyl Group ◽  
Side Chain ◽  
Compound I ◽  
Compound Ii

1. N-(5′-Phosphopyridoxyl)-l-glutamic acid (P-Pxy-Glu, compound I) is readily converted at pH3 into a substance (P-Pxy-Glp, compound II) characterized as N-(5′-phosphopyridoxyl)-2-oxopyrrolidine-5-carboxylic acid. 2. The u.v., i.r. and fluorescence spectra of P-Pxy-Glu and P-Pxy-Glp have been determined; from the u.v. spectra their pK values have been found and compared. 3. The apoenzyme of aspartate aminotransferase is rapidly and irreversibly inactivated by P-Pxy-Glu, but is inactivated more slowly by P-Pxy-Glp. The complex with P-Pxy-Glp is stable enough to be isolated, but it is slowly reactivated in the presence of excess of pyridoxal phosphate. 4. The u.v. spectrum of the complex of apoenzyme and P-Pxy-Glp suggests that it contains a hydrogen bond between the phenolic hydroxyl group and the pyrrolidone nitrogen; this specifies the conformation of most of the molecule of P-Pxy-Glp. This conformation is similar to that previously postulated for the enzyme–glutamate complex except for the side chain of glutamate. Hence both the affinity of P-Pxy-Glp for the apoenzyme and the fact that it is more easily removed than P-Pxy-Glu are explicable.

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