Jack beans, availability

Rat epididymis is also a good source of a-D-mannosidase, but it is not so readily available, in quantity, as jack-bean meal. A procedure similar to that just described was employed to obtain the enzyme from rat epididymis60 in the same state of purity as the jack-bean a-D-mannosidase, including freedom from /J-D-mannosidase and glycoaspartamidase. 

It has not been possible so far to establish that Cr is an essential element required by plants, however, addition of Cr to soils deficient in the element has been shown to increase growth rates and yields of potatoes, maize, rye, wheat or oats (Scharrer and Schropp, 1935 Huffman and Allaway, 1973 Bertrand and De Wolf, 1986). Nickel appears to be an essential element for plants (Farago and Cole, 1988). Zerner and coworkers (Dixon et al., 1975) demonstrated that urease isolated from jack bean (Canavalia ensiformis) was a nickel enzyme. Eskew et al. (1983) have shown that Ni is an essential micronutrient for legumes. Most plants contain nickel in the range 1 - 6 mg kg-1 (Vanselow, 1966 Hutchinson, 1981). The uptake of Ni is enhanced by low pH values, and available nickel increases at pH less than 6.5 as a consequence of the breakdown of Ni complexes in the soil with Fe and Mn oxides. Uptake of nickel by plants and questions of toxicity and tolerance have been reviewed by Farago and Cole (1988). Nickel toxicity toward plants has been reviewed by Vanselow (1966) and Hutchinson (1981). 

Fitting into the trend towards improvement of the availability and simplification the preparation of biocatalytic layers for biosensors, the use of crude materials has been explored. Arnold and coworkers investigated the feasibility of employing Jack bean meal in a urea sensor (Arnold and Glaizer, 1984) and rabbit muscle acetone powder in a sensor for adenosine monophosphate (Fiocchi and Arnold, 1984). Both sensors turned out to be serious contenders with the appropriate enzyme electrodes with respect to lifetime and slope of the calibration curves. Other parameters, such as response time and linear range, were quite similar. 

The starting material for the preparation of plant lectins is usually the seeds. They are either collected in the field or purchased from commercial sources. In some cases, seed meal is also available (e.g., jack bean or soybean flour). 

The volatile material to be estimated is placed in the outer annular compartment, the absorbent being in the inner compartment, where it is titrated subsequently without removal from the unit. The apparatus may be employed for the micro-estimation of ammonia, urea, chloride, bromide and carbonate, and for the detection of many volatile substances, such as alcohol, aldehydes and acetone. For details of the apparatus and its applications consult Conway, E. J. (1939), Micro-Diffusion Analysis. The various micro-methods available for the clinical estimation of urea are critically discussed by Lee and Widdowson Biochem. J., 1937, 31, 2035). The error arising from formation of ammonia by an enzyme-substrate system in jack bean urease extracts has been studied by Howell (1939), who reports that it can be eliminated by the use of extracts prepared five to twenty hotu-s before use, and by keeping the pH value of the digests between 6 and 6-6 by means of a citrate buffer. 

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