Antipyridoxine factors

A variety of plants and mushrooms contain pyridoxine (a form of vitamin B6) antagonists. The antipyridoxine factors have been identified as hydrazine derivatives.

Pyridoxine

(a form of vitamin B6)

Pyridoxine

(a form of vitamin B6)

Linseed contains the watersoluble and heat-labile antipyridoxine factor linatine. Linatine is y-glutamyl-1-amino-D-proline. It readily undergoes hydrolysis to the hydrazine derivative, 1-aminoproline, the actual antipyridoxine factor (Figure 3.4).

Antipyridoxine factors have also been found in wild mushrooms, the common commercial edible mushroom, and the Japanese mushroom shiitake. Commercial and shiitake mushrooms contain agaritine. Agaritine is hydrolyzed in the mushroom by y-glutamyl-transferase to the active agent 4-hydroxymethylphenylhydrazine (Figure 3.5). The hydrolysis of agaritine is accelerated if the cells of the mushrooms are disrupted. Careful

HOOC

N " COOH + Glutamic acid

Figure 3.4 Hydrolysis of linatine.

HOCH,

Agaritine

HOCH,

HOCH,

4 - (Hydroxymethyl)-phenylhydrazine

HOCH,

4 - (Hydroxymethyl)-phenylhydrazine

Glutamic acid

Figure 3.5 Hydrolysis of agaritine.

handling of the mushrooms and immediate blanching after cleaning and cutting can prevent hydrolysis.

The mechanism underlying the antipyridoxine activity is believed to be condensation of the hydrazines with the carbonyl compounds pyridoxal and pyridoxal phosphate — the active form of the vitamin — resulting in the formation of inactive hydrazones.

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