Genetic control of liver esterase forms in chickens

Six regions of esterase activity designated I to VI were resolved from liver extracts of chickens by horizontal starch gel electrophoresis. These esterases were further characterized on the basis of their substrate affinities and differential responses to various inhibitors.
Genetic variation was found in esterases of region VI which appeared to be ali-esterase. Four phenotypes, A, B, AB and O, were observed. These phenotypes were shown to be controlled by one autosomal locus, designated Es-3 , with alleles Es-3 ^A, Es-3 ^B and Es-3 ^O. This locus is not closely linked to the blood group loci A and B , serum alkaline phosphatase ( Ap ), liver acid phosphatase ( Acp-2 ) and serum esterase ( Es-1 ) loci.     

Genetic control of alkaline phosphatase isozymes in chicken duodenum

A genetic control of alkaline phosphatase (AP) in chicken duodenum was studied in a White Plymouth Rock strain. Unpurified chicken duodenum AP heated in an extraction procedure comprised either F or S band by isozyme types. On the other hand, chromatographically purified intestinal AP (NBCo, USA) had three bands, i.e., F', S' and B' bands. Characterization by urea, heat and neuraminidase treatments suggested that the genetic control of plasma AP isozymes may be applicable to the duodenum AP isozymes.     

Genetic control of extraglandular aromatase activity in the chicken

Feminization of feathers in the Sebright cock is the result of increase in the activity of skin aromatase. This increased estrogen synthesis is the consequence of an autosomal dominant mutation that causes an increase in the specific androgen-binding cytochrome P450 oxidase involved in the reaction. Since this oxidase appears to be kinetically indistinguishable from the activity in control ovary we believe that the mutation causes an increased steady-state level of normal enzyme. The mechanism by which the mutation acts is unknown, but its presence implies that in normal birds an allele of the mutation limits the activity of the enzyme in all tissues other than ovary.     

Unfolding and inactivation of fatty acid synthase from chicken liver during urea denaturation

The inactivation and conformational changes of the multifunctional fatty acid synthase (acyl-CoA:malonyl-CoA C-acyltransferase (decarboxylating, oxoacyl- and enoyl-reducing and thioester-hydrolyzing), EC 2.3.1.85) from chicken liver have been studied in urea solution. The results show that complete inactivation of the fatty acid synthase occurs before obvious conformational changes with regard to the overall, beta-ketoacyl reduction and acetoacetyl-CoA reduction reactions. Significant conformational changes indicated by the changes of the intrinsic fluorescence emission and the circular dichroism spectra occurred at higher urea concentrations. The kinetic rate constants for the two phase inactivation and unfolding reactions were measured and semilogarithmic plots of the activity versus time gave curves which could be resolved into two straight lines, indicating that both the inactivation and unfolding processes consisted of fast and slow phases as a first-order reaction. The results from Lineweaver-Burk plots indicated that urea is a competitive inhibitor for acetyl-CoA and malonyl-CoA, with K(m) increasing with increasing urea concentrations. However, urea is a noncompetitive inhibitor for NADPH, the substrate of the overall reaction and beta-ketoacyl reduction reaction, and acetylacetate, the substrate of the beta-ketoacyl reduction reaction. Activation by low concentrations of urea was observed although this activation was only temporarily induced in an early stage of inactivation. The aggregation phenomenon of the fatty acid synthase in a certain concentration range of urea (3-4 M) was also observed during unfolding. This result shows that this multifunctional enzyme unfolds with competition with misfolding in the folding pathway. Comparison of inactivation and conformational changes of the enzyme as well as aggregation imply that unfolding intermediates may exist during urea denaturation. The possible unfolding pathway of fatty acid synthase is also discussed in this paper.     

Nonspecific esterase and alpha-glycerolphosphate dehydrogenase activity and the fat content in the regenerating chicken liver]

The data on histochemical study of changes in the activity of esterases, alpha-glycerophosphate dehydrogenase and the fat content in the chick regenerating liver are presented. The accumulation of the fat in hepatocytes during the early periods of regeneration (1--5th day of the experiment) is partially conditioned by the reduction of the activity of nonspecific esterases. The maximal liver steatosis is accompanied also by an increase in the activity of alpha-glycerophosphate dehydrogenase which indicates intensification of glycolysis and synthesis of triacylglycerines (liver spare lipids) during regeneration.     

猪肝酯酶研究进展

猪肝酯酶是手性合成中重要的水解酶,对它的生化特性研究较早。近几年猪肝酯酶的基因克隆研究也取得了较大进展。重组酶具有选择特异性更高的特点,与生化提取方法相比成本较低廉。基因工程技术的开展使猪肝酯酶在化学工业、生物制药及相关领域中有了更加广泛的应用前景．     

Immunochemical characterization and biosynthesis of pI-6.4 esterase, a carboxylesterase of rat liver microsomal extracts.

Rat liver pI-6.4 esterase was purified from microsomes (microsomal extracts) and used to generate antibodies in the rabbit. Two active enzyme forms, similarly sensitive to endo-H (endo-beta-N-acetylglucosaminidase H (EC 3.2.1.96), but differing slightly in polypeptide chain length, were present in the preparation. In microsomes, immunoblots revealed a single form, with Mr congruent to 62,000, identical with the large component of the purified enzyme, indicating that the second component is an artefact. Rabbit reticulocyte lysates and wheat germ extracts programmed with RNA extracted from total or bound polysomes synthesized a single immunoreactive 61 kDa polypeptide, which was not formed with RNA extracted from free polysomes. The immunoreactive product synthesized in the presence of dog pancreas microsomes was slightly larger (62 kDa); like the authentic enzyme, it bound to concanavalin A and was decreased in molecular size to 60 kDa by the action of endo-H. Thus the enzyme is synthesized with a short cleavable sequence and bears at least one high-mannose oligosaccharide chain. Metabolic labelling in hepatocytes cultured with [35S]methionine also generated a single immunoreactive polypeptide of 62 kDa, which was decreased to 60 kDa in size by treatment with endo-H or addition of tunicamycin to the culture medium. This confirms the molecular homogeneity and the glycosylation of the enzyme in the intact cell. Culture media contained no pI-6.4-esterase-related protein, whether tunicamycin was present or not. The processing steps in the synthesis of pI-6.4 esterase are thus, as for other esterases of the endoplasmic reticulum [Robbi & Beaufay (1986) Eur. J. Biochem. 158, 187-194; (1987) Biochem. J. 248, 545-550] indistinguishable from those occurring early in the synthesis of secretory proteins. Glycosylation is apparently not the sorting signal responsible for their retention in the endoplasmic reticulum.     

On the control of arginine metabolism in chicken kidney and liver.

Arginases have been found to be located on the external side of the inner mitochondrial membrane of chicken kidney and liver. Transamidinase has been detected within the liver mitochondrial matrix space. Arginases and transamidinase act upon two different intracellular arginine pools. Penetration of arginine into the matrix space occurs only in respring mitochondria and in the presence of anions such as acetate and phosphate; D-arginine, L-ornithine, D-'ornithine and L-lysine penetrate with the same modalities. L-Histidine penetrates only kidney mitochondria. Because of transamidinase compartmentation, the rate of creatine synthesis is influenced by the rate of penetration of arginine into the mitochondria.     

Genetic variability for esterase enzyme in Onobrychis species

Summary Understanding polymorphism at the enzyme level is basic to its use in population and genetic studies. However, no such information is available on the variability among different sainfoin (Onobrychis) species. Therefore, our objective was to study the existence of genetic polymorphism for esterase in 17 Onobrychis species and three cultivars of O. viciifolia Scop. Three regions of banding were observed in all the materials tested, with the number of bands varying from 0 to 3, 3 to 14, and 1 to 2 bands in each of these zones, which have been designated EST1, EST2, and EST3 respectively. All the materials studied had unique banding patterns, the only common feature being that all of them, except one species, had isozyme 1. Identification was possible only for four species (O. iberica, O. kachetica, O. transcaucasica, and O. bieberstenii) and one cultivar (Nova) based on the banding patterns. Large diversity was evident from the wide range of percent similarity values (0%–79%). Subsequent studies should be directed in using these isozyme banding patterns as markers to the desirable agronomic and quality traits of different germplasm lines.This work was supported by USDA Specific Cooperative Agreement No. 58-7MN1-8-143 from the Plant Stress and Water Conservation Unit, USDA-ARS, Lubbock, Texas. Joint contribution of the Texas Tech University, Lubbock, Texas and the USDA-ARS. TTU Journal no. T-4-302