Different corrinoid specificities for cell growth and the cobalamin uptake system in Euglena gracilis z

Abstract

A variety of cobalamin analogues synthesized chemically or microbiologically were used to study the corrinoid specificities of cell growth and the cobalamin uptake system in Euglena gracilis z. Although Euglena could not utilize most of the analogues for cell growth, benzimidazolyl cobamide, cyanocobalamin-@'-phosphate, and cyanocobalamin-6-, -d-and -e-monocarboxylates had effects similar to that of cyanocobalamin on cell growth. It is suggested that Euglena cells have the ability to synthesize 'complete cobalamin' from the acid derivatives (amidation reaction) and/or the phosphate derivative (dephosphorylation reaction). Inhibition of uptake of radiolabelled cyanocobalamin caused by addition of various analogues indicates that both the d o w e r axial ligand (the cobalt-coordinated nucleotide) and the (6)-propionamide side-chain of the cobalamin molecule are essential for the cobalamin uptake system in Euglena. These results indicate that there are different corrinoid specificities for cell growth and the cobalamin uptake system in E. gradis z.

Effects of Vitamin B12Analogues with Alternations in the Side Chains of the Corrin Ring on Urinary Methylmalonate Excretion in Vitamin B12-Deficient Rats

“…Since CN-Cbl(l3-epi}·supple-men ted rats continuously excreted substantial amount of MMAin urine, AdoCbl(13-epi) ·would not function as a coenzyme of methylmaJonyl-CoA mutase. It has been reported that CN-Cbl(13-epi) cannot stimulate Escherichia coli and E. gracilis z growth, 7,15) and that AdoCbI(13-epi) is also inactive on AdoCbI-dependent dioldehydrase. 16 ) To bypass the process of the intestinal absorption of CbI, the CbI-deficient rats were injected intravenously with 500 ng of the CbI analogues every 24 h for 5 d. Urinary MMA excretion became undetectable 4 d after the administration of CN-Cbl or CN-Cbl(b-OR), but CN-Cbl(d-OR), CN-Cbl(e-OR), and CN-Cbl(l3-epi) did not affect urinary MMA excretion in the CbI-deficient rats (Fig.…”

“…Euglena gracilis z, a protozoan, has been reported to accumulate CN-Cbl(b-OH), (d-OH) and (e-OH) and to synthesize complete Cbl from the CN-Cbl acid derivatives, 7) suggesting the occurrence of the enzyme involved in the conversion of each of the acid derivatives to CN-Cbl (CN-Cbl monocarboxylic acid amide synthase) in this organism. There is little information available on whether mammalian cells contain the complete Cbl synthetic system found in E. gracilis z and how much the side chains of Cbl are involved in physiological roles and nutritional effects of Cbl in mammalian cells.…”

“…7) The revised structural assignments 10 • ll ) of the CN-Cbl(b-OH), CN-Cbl(d-OH), and CN-Cbl(e-OH) were used in the experiments because the assignments of the acid derivatives used in the experiments before·1980 were incorrect.…”

Biochemistry and Physiology of Vitamins in Euglena

“…The kinetics of CN-B12 uptake in Euglena are biphasic (Sarhan et al 1980) as in E. coli and Ochromonas malhamensis (Bradbeer 1971;Bradbeer and Woodrow 1976). The B12 structural specificities for cell growth and the B12 uptake system of Euglena were studied using a number of B12 analogues (Watanabe et al 1992). Euglena did not have the ability to utilize most of the B12 analogues for cell growth, whereas benzimidazolyl cyanocobamide and CN-B12 (b)-, (d)-, and (e)-monocarboxylates exerted similar effects on cell growth to that of authentic CN-B12.…”

Adenosylcobalamin-dependent methylmalonyl-CoA mutase isozymes in the photosynthetic protozoon Euglena gracilis Z

“…E. gradis 2 requires cobalamin (Cbl) for growth (Watanabe et al, 1992). It can take up and accumulate Cbl, which is converted into coenzymes 5'-deoxyadenosplc~balamin (AdoCblj and methylcobalarnin (lsegawa et a/., 1984).…”