I N THE PAST SEVERAL YEARS a number of radioassay procedures for serum vitamin B12 have been described. Each method is based on the fact that unlabeled crystalline B12 will competitively inhibit isotopically labeled B12 (tracer B12) from binding to a specific B12 binding protein(s). Basic to each procedure is the reaction of B12 (labeled and unlabeled) with a limited quantity of binding protein...

Adenosylcobalamin (Ado-B12) is both the cofactor and inducer of ethanolamine ammonia lyase (EA-lyase), a catabolic enzyme for ethanolamine. De novo synthesis of Ado-B12 by Salmonella enterica occurs only under anaerobic conditions. Therefore, aerobic growth on ethanolamine requires import of Ado-B12 or a precursor (CN-B12 or OH-B12) that can be adenosylated internally. Several known enzymes ade...

Objective: To determine prospectively plasma levels of vitamin B12 in diabetic patients with liver cirrhosis before and 3 months after vitamin administration and its effects on nutritional state of patients. Additionally study a new dosage form of vitamin B12 (buccal film) in compare to traditional one as intramuscular injection. Methods: 120 blood samples were collected from 60 adult cirrhotic...

I N THE PAST SEVERAL YEARS a number of radioassay procedures for serum vitamin B12 have been described. Each method is based on the fact that unlabeled crystalline B12 will competitively inhibit isotopically labeled B12 (tracer B12) from binding to a specific B12 binding protein(s). Basic to each procedure is the reaction of B12 (labeled and unlabeled) with a limited quantity of binding protein...

Ribonucleotide reductases (RNRs) catalyze the conversion of ribonucleotides to deoxyribonucleotides and are essential for de novo DNA synthesis and repair. Streptomycetes contain genes coding for two RNRs. The class Ia RNR is oxygen dependent, and the class II RNR is oxygen independent and requires coenzyme B12. Either RNR is sufficient for vegetative growth. We show here that the Streptomyces ...

A common polymorphism (775G>C) in the vitamin B12 transport protein, transcobalamin II (TCII), has been identified in which proline replaces arginine at codon 259. We determined the influence of TCII genotype on indices of B12 status, including total serum B12, the amount of B12 bound to TCII (holoTCII), methylmalonic acid, and homocysteine, in 128 healthy older adults (ages 40-88 years). Mean ...

T FIAT VITAMIN B12 IN SERUM is l)ound to protein14 has been known since shortly after the isolation of the vitamin. Endogenous vitamin B12 (which may be mainly methyl-Bi2) is bound primarily to an a1-globulin 2.6-10 hut vitamin B12 added to serum in vitro hinds primarily to -globuun (presumably because B12-binding a-globulin is normally almost saturated with endogenous vitamin B12).61#{176} hal...

Complete B12 derivatives are natural "molecular switches" as a result of the coordinative switch ("base on" or "base off") of the natural nucleotide base. Certain predesigned B12-nucleotide conjugates were shown recently to behave as "retro riboswitches", in which the nucleotide environment modified the equilibrium between these two isomeric B12 structures. In contrast, the "reverse" situation ...

BACKGROUND There is a growing focus on nutritional therapy for Alzheimer's disease (AD), and controversy exists regarding the association between AD and homocysteine (Hcy), vitamin B12, and folate levels. OBJECTIVE The present study evaluated the association between AD and the combined levels of Hcy, vitamin B12, and folate. METHODS This case-control study consisted of 115 patients with AD ...

Substantial amounts of vitamin B12 were found in some edible algae (green and purple lavers) and algal health food (chlorella and spirulina tablets) using the Lactobacillus delbrueckii subsp. lactis ATCC7830 microbiological assay method. Corrinoid-compounds were purified and characterized from these algae to clarify the chemical properties and bioavailability of the algal vitamin B12. True vita...