Schiff base formation by the lysyl and hydroxylysyl side chains of collagen

Glycated serum proteins: High in pancreatic cancer and low in preeclampsia

Glycated serum protein (GSP, measured as serum fructosamine concentration in μmol/L) is a product of glycation reaction between glucose and serum proteins in the blood circulation. GSP is used along with blood glucose, glycated hemoglobin (HbA1c), and glycated albumin as indicators of glycemic control for diabetic patients. However, a systematic comparison of the GSP levels in different types of human diseases has not been reported. In this study, 62,698 clinical lab test results of GSP levels in patients with 61 clinically defined diseases over the past 5 years in our hospital were retrieved and compared to that of 1861 clinical lab test results in healthy individuals. Based on the mean (SD), median, and p (-Log₁₀p) values, we found that patients with type 2 diabetes, hepatic encephalopathy, pancreatic cancer, healthy individuals >65 years old, and cerebral arteriosclerosis had significantly (p<0.05, -Log₁₀p>1.30) increased whereas patients with 49/61 diseases including preeclampsia, nephrotic syndrome, sepsis, lupus erythematous, and leukemia had significantly decreased GSP levels compared to that of healthy controls. Among the 61 diseases, type 2 diabetes and leukemia had the highest -Log₁₀p values (>274) and lupus erythematous, nephrotic syndrome, and gastric cancer had -Log₁₀p values >140. Revealing the molecular mechanisms especially those underlying the decreased GSP levels in most of human diseases might make GSP levels serve more clinical purposes in future.

Isolation of animal cell mutants defective in long-chain fatty aldehyde dehydrogenase. Sensitivity to fatty aldehydes and Schiff's base modification of phospholipids: implications for Sj-ogren-Larsson syndrome

Using tritium suicide, we have isolated a variant of the Chinese hamster ovary cell line, CHO-K1, that is deficient in long-chain fatty alcohol:NAD+ oxidoreductase (FAO; EC 1.1.1.192). Specifically, it was the fatty aldehyde dehydrogenase component that was affected. The enzymatic deficiency found in this mutant strain, designated FAA. K1A, was similar to that displayed by fibroblasts from patients with Sjögren-Larsson syndrome (SLS), an inheritable neurocutaneous disorder. Complementation analyses suggested that the deficiency in fatty alcohol oxidation in the FAA.K1A cells and the SLS fibroblasts is a result of lesions in homologous genes. The FAA.K1A cells were unable to convert long chain fatty aldehydes to the corresponding fatty acids. This resulted in a hypersensitivity of the FAA.K1A cells to the cytotoxic effects of long chain fatty aldehydes. The difference between the mutant and wild-type cells was most obvious when using fatty aldehydes between 14 and 20 carbons, with the greatest difference between wild-type and mutant cells found when using octadecanal. Fibroblasts from a patient with SLS also displayed the hypersensitivity phenotype when compared with FAldDH+ human fibroblasts. In both CHO and human FAldDH- cell lines, addition of long chain fatty aldehydes to the medium caused a dramatic increase in aldehyde-modified phosphatidylethanolamine, presumably through Schiff's base addition to the primary amine of the ethanolamine head group. When 25 microM hexadecanal was added to the growth medium, approximately 10% of the phosphatidylethanolamine was found in the fatty aldehyde-modified form in FAA.K1A, although this was not observed in wild-type cells. Modified phosphatidylethanolamine could be detected in FAldDH- cells even when exogenous fatty aldehydes were not added to the medium. We propose a possible role for fatty aldehydes, or other aldehydic species, in mediating some of the symptoms associated with Sjögren-Larsson syndrome.

Some properties of the reactive hydroxylysyl residues in collagen: their possible role in nucleation during fibril formation

Native or heat-denatured collagens were incubated under controlled conditions of temperature and pH with variable molar ratios of KCNO or 2,4,6-trinitrobenzene sulphonic acid. The results obtained suggest that a small number of free amino groups are available for reaction on the native protein, while all the free amino groups react on the denatured protein. The highly reactive free amino groups in the native protein are hydroxylysine residues and have an abnormally low pK of 8.5 which is conformation dependent; this pK becomes normalized upon denaturation of the protein. The reactive hydroxylysines appear to be located in basic regions that could be the nucleation sites needed for fiber formation in the heat-gelation assay; the modified protein does not form stable fibrils upon heating at 37 degrees C and the few fibers formed are not stabilized after reduction with NaBH4. Our results also suggest that the triple helix in collagen is heterogeneous with respect to the reactivity of free amino groups and that several discrete transition temperatures are observed with two main breaks at 30 degrees C and at 37 degrees C, respectively.