Zinc as modulator of oxygenation function and stabilizer of quaternary structure in earthworm hemoglobin

Molecular Shape, Dissociation, and Oxygen Binding of the Dodecamer Subunit of Lumbricus terrestris Hemoglobin

“…It is appropriate to note that group IIA cations stabilize the quaternary structure of Lumbricus Hb to apparently similar extents, inhibiting dissociation, whether at alkaline pH or at neutral pH and promote reassembly to the HBL structure (12). The oxygenation parameters obtained for Hb in the absence and presence of Ca 2ϩ are in general agreement with earlier findings (36) and results obtained with other earthworm Hbs (37,38). The differences between P 50 and P m (Table VI) are greater for both dodecamer preparations than for blood or Hb and are due to asymmetry in the O 2 binding curves (Fig.…”

“…The effect of 100 mM Ca 2ϩ or Mg 2ϩ is to increase the n 50 of blood, Hb, and dodecamer by 20 -40%. Since the concentration of these ions in earthworm plasma is Յ10 mM (38), it is unlikely that the difference in the n 50 for blood and Hb could be due to cation effects.…”

Effects of Magnesium and Calcium on the Oxygenation Reaction of Erythrocruorin from the Marine Polychaete Arenicola marina and the Terrestrial Oligochaete Lumbricus terrestris

“…In Lumbricus, the value begins to increase from -0.4 at 5 mM Mg and Ca, then reaches the maximum value of -0.75 at 40 mM Mg and Ca, and maintains the same value above 40 mM Mg and Ca. Ca concentration in the blood is about 10 mM in both Arenicola and Lumbricus, while Mg concentration is far higher in Arenicola than in Lumbricus (55 mM and 2-4 mM, respectively: Kamemoto et al, 1962;De Jorge et al, 1965; Sawaya, 1967;Prosser, 1973;Oglesby, 1978;Ochiai et al ., 1993). Here again we try to compare the reactivity of both Ers to each cation under their physiological concentrations.…”

“…Especially in Lumbricus Er, each value is somewhat higher than that of the Ca reported by Standley et al . (1988) and those of the Mg and Ca for Pheretima hilgendorfi (Ochiai et al ., 1993), respectively. This may simply be due to the fact that dialysis step was omitted in this preparation, however, their numerical values may indicate the specific affinity of Ca for the Er.…”

“…In Marphysa sanguinea , Er appears to be insensitive to Mg and Ca (Imai et al ., 1990), as is observed with Eurythoe complanata Er and Mg (Ilan et al ., 1990). In oligochaetes, on the other hand, Ca is more effective than Mg in almost all species examined, as Eisenia foetida (Ochiai, 1984;Igarashi et al ., 1985;Igarashi et al ., 1991), Lumbricus terrestris (Fushitani et al ., 1986), and Pheretima hilgendorfi (Ochiai et al ., 1993). However, in Glossoscolex paulistus , Mg and Ca exert the same effect on the affinity at the physiological range (Marques and Meirelles, 1995).…”