Hydrolysis of RNA to 5′‐nucleotide by seed sprouts, particularly malt sprouts

Conditions for the efficient conversion of commercial RNA to nucleoside 5′‐monophosphate by means of a phosphodiesterase in malt sprouts have been determined. A comparison of the enzyme content of the rootlets, stems, and kernels of various plant seedlings, including barley, rye, oat, wheat, rice, and beans shows maximum amounts in the rootlets, and minimum quantities in the ungerminated kernels. Of all the seedlings tested, (mung bean, soy bean, oat, wheat, rice, barley) barley gave the highest conversion of RNA to 5′‐nucleotides. Commercial malt sprouts prepared from 6 different malted barleys including 2‐rowed and 6‐rowed samples all showed about the same amount of phosphodiesterase content. Besides phosphodiesterase, other enzymes capable of hydrolyzing RNA and 5′‐nucleotides were found in sprouts. These included 3′‐phosphodiesterases, 5′‐nucleotidases, and nucleosidases. By carefully pretreating both extracts and the solid sprouts at elevated temperatures for a limited time and by the addition of minimum amounts of Zn +2 , the action of these undesirable enzymes was either effectively destroyed or minimized so that the production of 5′‐nucleotides was maximized. It was found that suspensions of appropriately washed and treated barley malt rootlets are substantially more effective than aqueous extracts for converting RNA to 5′‐nucleotides.