Comparative Biochemistry and Physiology Part B: Comparative Biochemistry最新文献

Eggs from Marthastherias glacialis exert antibacterial action on marine bacterial strains and show a lysozyme-like activity. This one depends on pH and ionic strength of sample and reacting medium. This hydrolase, purified by gel filtration and ion-exchange chromatography, could be responsible for the bacterial growth inhibitory activity observed.

The metabolism of glutamine (Gln) and glucose was studied in intraepithelial lymphocytes (IEL) from 21-, 29- and 56-day-old pigs. Pigs were weaned at 21 days of age. Cells were incubated at 37°C in the presence of Krebs-Ringer bicarbonate buffer (pH 7.4) containing 1 mM [U¹⁴C]glutamine plus 5 mM glucose, or 5 mM [U¹⁴C]glucose plus 1 mM glutamine. Glucose was converted to lactate, pyruvate and CO₂, which accounted for 81, 11 and 8% of measured glucose carbon, respectively. Glutamine was metabolized mainly to glutamate (92% of Gln C) and ammonia, and to a lesser extent, to aspartate (4% of Gln C) and CO₂ (4% of Gln C). In the presence of both glucose and glutamine, glucose provided 2–3-fold more ATP to IELs than glutamine in 21–56-day-old pigs, on the basis of their measured end products. The rates of ammonia and glutamate production from glutamine in IELs from 29-day-old pigs were 112 and 90% greater than those in cells from 56-day-old pigs, respectively. The rates of glucose oxidation to CO₂ in IELs from 29-day-old pigs were elevated 56 and 64% respectively, compared with 21- and 56-day-old pigs. Elevated rates of substrate metabolism in IELs from 29-day-old post-weaning pigs indicated a metabolic alteration of these cells possibly due to changes in diet and intestinal bacterial population.

Two female-specific serum proteins (FSSPs) were detected immunologically in estradiol-treated Japanese sardine Sardinops melanostictus. The major FSSP was demonstrated to be a high molecular estradiol-inducible glycolipophosphoprotein with an immunological relation to a major yolk protein, and was suggested to be vitellogenin (VTG). VTG was purified using negative immunoaffinity chromatography. The isolated VTG was used for raising the specific antiserum against VTG. A homologous enzyme-linked immunosorbent assay (ELISA) was developed using the antiserum and the isolated VTG. The sensitivity range of the ELISA was 44 ng/ml to 2670 ng/ml of VTG concentration for the conditions used in our investigation.

The first thermophilic eubacterial glutamate dehydrogenase was purified to homogeneity from Bacillus acidocaldarius to compare its molecular properties with those of the glutamate dehydrogenase from thermophilic archaea. Glutamate dehydrogenase represents 2% of the total soluble proteins of B. acidocaldarius, an amount that may suggest an important role for this enzyme in nitrogen metabolism of the thermophilic eubacterium. The protein is a hexamer (subunit mass 48 kDa) and undergoes dissociation during gel filtration analysis. Isoelectric focusing of the purified enzyme indicated a pI of 4.5. The enzyme is strictly specific for NAD, 2-oxoglutarate, and l-glutamate. The thermal stability of B. acidocaldarius glutamate dehydrogenase is dependent on protein concentration.

Babesia hylomysci was found to contain two superoxide dismutase (SOD) isoenzymes with isoelectric points (pI) of 4.9 and 5.2. The two isoenzymes (45 and 47 kDa) were composed of two subunits of 22 kDa. An unique amino terminal sequence was determined up to 34 residues from the pooled isoenzymes and was identified as a sequence of SOD. The comparison of this N-terminal sequence of B. hylomysci SOD with 29 known Fe- or Mn-SODs showed more homologies with Fe-SODs.

An α-amylase that hydrolyzes unmodified starch or amylopectin azure was demonstrated in crude and partially purified extracts prepared from whole carcasses of sweetpotato whiteflies (SPW) (Bemisia tabaci Genn.).

All nymphal instars and adult SPW, including newly eclosed crawlers that had not yet fed on plant materials, were found to have active α-amylase. α-Amylase activity per mg protein was greatest in 1st instars and decreased with age up to the “pupal” stage, with a very slight increase in activity in adults. However, activity per individual did not differ substantially as a function of age.

The α-amylase had an apparent molecular weight of about 70 kDa, an isoelectric point of 6.32 and eluted with about 250 mM NaCl from a strongly basic anion-exchange column.

The enzyme activity was inhibited by EDTA and not activated by either NaCl or KNO₃. CaCl₂ strongly enhanced activity.

α-Amylase activity was greatest at pH 7.0, but there was considerable activity at pHs above 7.0.

The K_m of the α-amylase was 1.47 Mm with p-nitrophenyl α-d-malto-heptaoside as substrate.

The presence of an amylolytic enzyme in a phloem-feeding insect is unexpected and raises questions about current assumptions of feeding behavior of this species.

Glutathione S-transferases have been partially characterised from the gastrointestinal nematode Heligmosomoides polygyrus. Two major subunit families were purified (24 and 23 kDa) with N-terminal homology to the mammalian Alpha family. Four dimeric forms of GST were purified from the nematode by glutathione-affinity chromatography, two major enzymes (pI 8.1, 5.0) and two minor forms (pI 5.8, 5.3). The purified GST pool could neutralize model and lipid peroxides via peroxidase activity but not peroxidation derived reactive carbonyls via glutathione transferase activity. Antisera raised to the pooled nematode GSTs appeared to recognize other Strongylida GSTs more strongly on Western blotting compared to mammalian GSTs.

A cultured fish cell line, CE, derived from Oryzias celebensis, which lives in a tropical zone, was more heat-resistant than the OL32, which were derived from the Japanese medaka, Oryzias latipes which lives in a temperate zone. Protein synthesis in OL32 cells was also more heat-sensitive than that in CE cells. The relative levels in proteins of the HSP70 family and the ability of cells to tolerate severe heat treatment after a conditioning heat treatment were examined. Twenty-four hours after conditioning heat treatment, both cell lines retained thermotolerance even though three proteins in the HSP70 family had returned to their control levels.

The relationship between ovarian steroidogenesis and the development of oogenesis was studied in the ovary of Trichogaster trichopterus by histological examination and thin layer chromotography. The percent yield of 17β-estradiol (E₂) was high at a number of different stages of vitellogenesis, while those of 17α,20β-dihydroxy-4-pregnen-3-one (17,20-P) and testosterone (T) were high at the beginning of maturation, and increased steadily during this process. The per cent yields of T and 17α-hydroxyprogesterone (17-P) were low at all stages of vitellogenesis (VTG). For androstenedione (AS), 5-androstane-3β-ol-17-one, 5β-pregnane-3α,17α,20α-triol and 11-ketotestosterone, the per cent yields appeared to increase mainly during maturation and ovulation. It is suggested that the main pathways of steroidogenesis during oogenesis are: at VTG, [P]→[17-P]→[AS]→[E₂]; and at maturation [17-P] → [17,20-P], the latter controlled by male stimulation of GtH.