| Popis: |
Kallikrein digestion of human low density lipoproteins (LDL) has recently been shown to result in the degradation of apolipoprotein B (apo-B) into four major fragments, two of them being B-26 and B-74, which have been reported to be present in the LDL of some individuals. We studied the binding of kallikrein-treated LDL to human fibroblasts; digestion did not affect binding. Digested LDL was not taken up by macrophages, showing that it behaved like normal LDL. The activation of acyl-CoA cholesterol acyltransferase by LDL in fibroblasts was also not altered by kallikrein digestion. When delipidated LDL was treated with kallikrein, apo-B was digested into very small fragments, indicating that kallikrein can cleave apo-B at sites other than those which result in the formation of B-26 and B-74. The partial delipidation of LDL with heptane also resulted in more extensive digestion of apo-B, although binding to cells was unaffected. These studies suggest that the cholesterol core maintains the proper orientation of apo-B in the LDL particle and that kallikrein may be used as a tool to elucidate the association of apo-B and lipids in the LDL particle. |
