Methods are described for the in vitro cultivation of theexcised lupin embryo on a synthetic medium.
The postulate that asparagine synthesis is not conditionedprimarily by the presence of excess free ammonia and hence is not adetoxication mechanism has been experimentally confirmed in the lupin.
Isolated embryos, when supplied with adequate carbohydrate andnitrogen in the medium, are unable to absorb and convert succinic,malic, pyruvic, lactic, and glyceric acids, and glycerol and succinmonamideto asparagine.
Under similar conditions of carbohydrate and nitrogen supplyfumaric, maleic, aspartic, exalacetic, and glutamic acids, andsuccindiamide are effective in stimulating the synthesis of asparagine.Of these compounds; glutamic adid is the most effective.Metabolic products of glutamic acid such as ketoglutaric, glutaric,and succinic acids are not effective. Combinations of glutamic acidwith aspartic and oxalacetic acids in the absence of ammonia arelikewise not effective in the stimulation of asparagine synthesis.
An extract of embryo tissue is able to oxidize glutamic acidin the presence of boiled yeast juice. Amide formation has beendemonstrated in such an extract to which was added glutamic andaspartic acids and ammonia.
An attempt has been made to unify the above observations, andto explain the role of glutamate as an energy source in asparaginesynthesis, with the energy transfer possibly taking place throughthe intermediation of a pyridine coenzyme.
The unsatisfactory status of the postulated conversion ofaspartic acid to asparagine has been pointed out and a scheme proposedto explain the introduction of energy into the system.
