. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. X ui MG PROTEIN ADOEO 6^5 150 450 750 1050 mMOLES RuBP/L 1350 Figure 4. Enzyme proportionality and substrate saturation curves of ribulose 1,5-bisphosphate car- boxylase (RuBPCase). Ribulose 1,5-bisphosphate becomes inhibitory at concentrations exceeding mA/. resulting in an approximate K^ and V^ax of mM and units/g, respectively for the uninhibited portion of the curve. Km and Vmax- Phosphoribulokinase, a second enzyme of the Calvin-Benson cycle, catalyzes the phosphorylat
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. X ui MG PROTEIN ADOEO 6^5 150 450 750 1050 mMOLES RuBP/L 1350 Figure 4. Enzyme proportionality and substrate saturation curves of ribulose 1,5-bisphosphate car- boxylase (RuBPCase). Ribulose 1,5-bisphosphate becomes inhibitory at concentrations exceeding mA/. resulting in an approximate K^ and V^ax of mM and units/g, respectively for the uninhibited portion of the curve. Km and Vmax- Phosphoribulokinase, a second enzyme of the Calvin-Benson cycle, catalyzes the phosphorylation of ribulose-5-phosphate to ribulose 1,5-bisphosphate, and activity of this enzyme was also present in gill homogenates (Fig. 6). The activity was proportional to the amount of homogenate added, and a double reciprocal plot yielded a K^ of mM for ribulose-5-phosphate and a Vma^ of units/g wet weight. The presence of these two enzymic activities is consistent with a potential for net CO2 fixation in vivo in the gill tissue. Results of our enzymatic analyses for APS reductase and ATP sulfurylase are given in Figure 5. APS reductase catalyzes the production of adenosine phosphosulfate from AMP and sulfite, and a double reciprocal plot gave a Vmax of units/g and a Km value of /iM for sulfite. ATP sulfurylase phosphorylates adenosine phos- phosulfate to form ATP and sulfate; Vmax and Km values were units/g wet weight gill tissue and fiM, respectively. Strong enzyme proportionality was observed for both activities. Although the enzyme rhodanese is not as reliable an indicator of sulfur-based energy metabolism as the two enzymes above, it is noteworthy that we were able to qualitatively demonstrate the presence of this enzymic activity in gill homogenates also. However, since the assay technique did not give linear reaction rates we cannot report a quantitative value. Finally, nitrite reductase, which catalyzes the ferredoxin-dependent formation of ammon
Size: 1637px × 1526px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauth, bookcentury1900, booksubjectbiology, booksubjectzoology
