Kinetcs and decay of fumarase activity of immobilized Brevibacterium ammoniagenes cells for continuous production of L-malic acid

The kinetics of the reversible fumarase reaction of immobilized Brevibacterium ammoniagenes cells and the decay behavior of enzyme activity were investigated in a plug flow system. The time course of the reaction in the immobilized cell column was well explained by the time-conversion equation including the apparent kinetic constants of the immobilized cell enzyme. The decay rate of fumarase activity was faster in the upper sections of the column (inlet side of the substrate solution) compared with the lower sections when 1M sodium fumarate (pH 7.0) was continuously passed through the column at 37°C. It was shown that the decay rate of the fumarase activity in the immobilized cell column depends on the flow rate of the substrate solution. The effect of flow rate on the decay rate of enzyme activity was considered to be related to the rate of contamination of enzyme with poisonous substances derived from the substrate solution or to the rate of leakage of enzyme stabilizers and/or enzyme itself from the immobilized cells.     

Genetic analysis of variation in the number of primary spermatocytes per cyst in Drosophila virilis

Two experiments were performed with the aim of clarifying the genetic basis of variation in the number of primary spermatocytes per cyst in the B12 strain of Drosophila virilis and identifying the chromosome responsible for the variation. First, crosses between B12, showing a mean cell number of 11.81, and strain TK with a mean of 7.91, were performed. From the results obtained, it was considered that there were two factors, i.e., a recessive gene and certain modifiers, which shifted the cell number toward a higher value in B12. Second, chromosomal analysis with a marker strain and the B12 strain revealed that the third chromosome of B12 was responsible for the major effect of changing the primary spermatocyte number, although this chromosome did not exert a sufficient effect alone, and furthermore that at least one of the modifiers located on the second chromosome.     

Enzymatic synthesis of poly-β-hydroxybutyrate inZoogloea ramigera

The enzyme activity synthesizing poly--hydroxybutyrate (PHB) was mainly localized in the PHB-containing particulate fraction ofZoogloea ramigera I-16-M, when it grew flocculatedly in a medium supplemented with glucose. On the other hand, the enzyme activity remained in the soluble fraction, when the bacterium grew dispersedly in a glucose-starved medium.The soluble PHB synthase activity became associated with the particulate fraction as PHB synthesis was initiated on the addition of glucose to the dispersed culture. Conversely, the enzyme activity was released from the PHB-containing granules to the soluble fraction when the flocculated culture was kept incubated without supplementing the medium with glucose.PHB synthase was also incorporated into the newly formed PHB fraction when partially purified soluble PHB synthase was incubated withd(-)--hydroxybutyryl CoA in vitro.Although attempts to solubilize the particulate enzyme were unsuccessful, and the soluble enzyme became extremely unstable in advanced stages of purification, both PHB synthases had the same strict substrate specificity ford(-)--hydroxybutyryl CoA, and showed the same pH optimum at 7.0.Non-Standard Abbreviations PHB poly--hydroxybutyrate     

Modulation of synaptic plasticity by brain estrogen in the hippocampus

The hippocampus is a center for learning and memory as well as a target of Alzheimer's disease in aged humans. Synaptic modulation by estrogen is essential to understand the molecular mechanisms of estrogen replacement therapy. Because the local synthesis of estrogen occurs in the hippocampus of both sexes, in addition to the estrogen supply from the gonads, its functions are attracting much attention.