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Angiotensin I-converting enzyme (ACE), a dipeptidyl carboxypeptidase, catalyzes the conversion of Angiotensin I to the potent vasoconstrictor Angiotensin II and plays an important physiological role in regulating blood pressure. Inhibitors of angiotensin 1-converting enzyme derived from food proteins are utilized for pharmaceuticals and physiologically functional foods. ACE inhibitory properties of different enzymatic hydrolysates of glycinin, the major storage protein of soybean, have been demonstrated. The IC50 value for the different enzyme digests ranges from 4.5 to 35 microg of N2. The Protease P hydrolysate contained the most potent suite of ACE inhibitory peptides. The ACE inhibitory activity of the Protease P hydrolysate after fractionation by RP-HPLC and ion-pair chromatography was ascribed to a single peptide. The peptide was homogeneous as evidenced by MALDI-TOF and identified to be a pentapeptide. The sequence was Val-Leu-Ile-Val-Pro. This peptide was synthesized using solid-phase FMOC chemistry. The IC50 for ACE inhibition was 1.69 +/- 0.17 microM. The synthetic peptide was a potent competitive inhibitor of ACE with a Ki of 4.5 +/- 0.25 x 10(-6) M. This peptide was resistant to digestion by proteases of the gastrointestinal tract. The antihypertensive property of this peptide derived from glycinin might find importance in the development of therapeutic functional foods.

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BackgroundDiabetic ketoacidosis (DKA) is characterized by a biochemical triad of hyperglycemia, acidosis, and ketonemia. This condition is life-threatening despite improvements in diabetic care. The purpose of this study was to evaluate the clinical and biochemical prognostic markers of DKA. We assessed correlations in prognostic markers with DKA-associated morbidity and mortality.MethodsTwo hundred and seventy patients that were hospitalized with DKA over a period of 2 years were evaluated clinically and by laboratory tests. Serial assays of serum electrolytes, glucose, and blood pH were performed, and clinical outcome was noted as either discharged to home or death.ResultsThe analysis indicated that significant predictors included sex, history of type 1 diabetes mellitus or type 2 diabetes mellitus, systolic blood pressure, diastolic blood pressure, total leukocyte count, Acute Physiology and Chronic Health Evaluation II (APACHE II) score, blood urea nitrogen, serum creatinine, serum magnesium, serum phosphate, serum osmolality, serum glutamic oxaloacetic transaminases, serum glutamic pyruvic transaminases, serum albumin, which were further regressed and subjected to multivariate logistic regression (MLR) analysis. The MLR analysis indicated that males were 7.93 times more likely to have favorable outcome compared with female patients (odds ratio, 7.93; 95% confidence interval, 3.99 to 13.51), while decreases in mean APACHE II score (14.83) and serum phosphate (4.38) at presentation may lead to 2.86- and 2.71-fold better outcomes, respectively, compared with higher levels (APACHE II score, 25.00; serum phosphate, 6.04).ConclusionSex, baseline biochemical parameters such as APACHE II score, and phosphate level were important predictors of the DKA-associated mortality.

The three-dimensional structures of human and rabbit liver cytosolic recombinant serine hydroxymethyltransferases (hcSHMT and rcSHMT) revealed that E75 and Y83 (numbering according to hcSHMT) are probable candidates for proton abstraction and Ca-Cb bond cleavage in the reaction catalyzed by serine hydroxymethyltransferase. Both these residues are completely conserved in all serine hydroxymethyltransferases sequenced to date. In an attempt to decipher the role of these residues in sheep liver cytosolic recombinant serine hydroxymethyltransferase (scSHMT), E74 (corresponding residue is E75 in hcSHMT) was mutated to Q and K, and Y82 (corresponding residue is Y83 in hcSHMT) was mutated to F. The specific activities using serine as the substrate for the E74Q and E74K mutant enzymes were drastically reduced. These mutant enzymes catalyzed the transamination of d-alanine and 5,6,7,8-tetrahydrofolate independent retroaldol cleavage of l-allo threonine at rates comparable with wild-type enzyme, suggesting that E74 was not involved directly in the proton abstraction step of catalysis, as predicted earlier from crystal structures of hcSHMT and rcSHMT. There was no change in the apparent T m value of E74Q upon the addition of l-serine, whereas the apparent T m value of scSHMT was enhanced by 10 8C. Differential scanning calorimetric data and proteolytic digestion patterns in the presence of l-serine showed that E74Q was different to scSHMT. These results indicated that E74 might be required for the conformational change involved in reaction specificity. It was predicted from the crystal structures of hcSHMT and rcSHMT that Y82 was involved in hemiacetal formation following Ca-Cb bond cleavage of l-serine and mutation of this residue to F could lead to a rapid release of HCHO. However, the Y82F mutant had only 5% of the activity and failed to form a quinonoid intermediate, suggesting that this residue is not involved in the formation of the hemiacetal intermediate, but might be involved indirectly in the abstraction of the proton and in stabilizing the quinonoid intermediate.

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