Putative pyrophosphate phosphofructose 1-kinase genes identified in sugar cane may be getting energy from pyrophosphate

Pyrophosphate-dependent phosphofructokinase (PPi-PFK) has been detected in several types of plant cells, but the gene has not been reported in sugar cane. Using Citrus paradisi PPi-PFK gene (AF095520 and AF095521) sequences to search the sugar cane EST database, we have identified both the alpha and beta subunits of this enzyme. The deduced amino acid sequences showed 76 and 80 similarity with the corresponding alpha and beta subunits of C. paradisi. A high degree of similarity was also observed among the PFK b subunits when the alignment of the sugar cane sequences was compared to those of Ricinus communis and Solanum tuberosum. It appears that alpha and beta are two distinct subunits; they were found at different concentrations in several sugar cane tissues. It remains to be determined if the different gene expression levels have some physiological importance and how they affect sucrose synthesis, export, and storage in vacuoles. A comparison between the amino acid sequences of b PFKs from a variety of organisms allowed us to identify the two critical Asp residues typical of this enzyme's activity site and the other binding sites; these residues are tightly conserved in all members of this protein family. Apparently, there are catalytic residues on the b subunit of the pyrophosphate-dependent enzyme

Preliminary report on the short stature of Southeast Asian forest dwellers, the Manni, in southern Thailand: lack of an adolescent spurt in plasma IGF-I concentration.

Plasma concentration of insulin-like growth factor type-I (IGF-I) was studied among the Mannis in Thailand to find a possible cause of their short stature. The Mannis are hunting and gathering indigenous tribal peoples living in Asian tropical rain forests. A total of 50 plasma specimens from three different Manni groups in southern Thailand were used in this study. The concentrations of acid-ethanol extract of plasma IGF-I were measured by radio-immunoassay. We found that (1) plasma concentration of IGF-I in the Mannis was low, (2) there was no adolescent spurt in IGF-I levels, and (3) the post adolescent plasma IGF-I level of the Manni was significantly lower than that of age-matched Japanese. Low IGF-I levels among the Mannis may account for their short stature.